Forza Win, 133 Copeland Road, London SE15 3SN (020 7732 9012). Meal for two, including drinks and service £60-£120

I have eaten my lunch in toilets. This is not scatological hyperbole. There are a bunch of gentlemen’s conveniences that have been upcycled into bars and cafés, where you might sit with your knees in the now-polished urinals, blowing the froth off a flat white while clutching a soft bap. Restaurants have been opened in old power stations and butcher’s shops; in churches that God obligingly has moved out of to make space for the Josper grill, and in enough shipping containers to fill a Maersk liner.

You’d think we’d be used to it by now, this post-high-street hospitality, but we’re not. The concept of the restaurant – what it should look like, the kind of space it should occupy, the way it should feel – is extraordinarily robust. Those intriguing repurposed spaces remain the minority among restaurateurs and the authorities who license them. The result is our stubbornly identikit high streets offering endless, will-sapping permutations of Byron-Côte-Wagamama-Zizzi-Jamie’s-Italian-Burger.

And it’s self-fuelling. Each time such a space becomes available, the “cookie cutter” chains pile in, offering landlords the impression of security, even in these days of multiple branch closures. In turn, those landlords appear to assume that if it’s tough for the chains, with their economies of scale, and their brutal ways of wringing every last penny of profit margin out of the garlic bread, how much harder must it be for the independent operators diverting from the mainstream?

Give thanks then for the enlightened licensing officers who have enabled Forza Win to flourish in their knackered warehouse on a south London industrial estate. Here, in Peckham, the walls are not so much distressed as ready for an intense course of cognitive behavioural therapy or perhaps just a hug. If you love ducting, corrugation and slab concrete, this is the place for you. You are unlikely to walk in off the street. You’ll only come here because you were intending to. You really should.

Until last October, Forza Win was a ramshackle “let’s put the show on right here in the barn” affair, shaped for its space: you bought tickets in advance. You sat at communal tables and ate from an Italian-accented set menu. I went once, on a cold winter’s night, when it felt like the only warmth was from the encouraging food. Halfway through dinner, a server dropped a carving knife down my back as if subconsciously they wanted to stab me, which is unimaginable. Who in the restaurant business would wish me harm?

Now they have fitted an open kitchen, some shiny tables rather than the creaky splintered ones they used to have and instituted a classic Italian menu. It operates as a standard restaurant and is run by delightful staff who would never try to stab a restaurant critic in the back. Three of us visit on a hot Sunday lunchtime, when fans are beating the warm air about the vault, and the space is filled with rattling, happy chatter and the clatter of plates. We drink glasses of a long, sour lemon punch and grin at the single sheet of paper in our hands.

There are half a dozen antipasti, three pasta dishes and four mains. What’s most striking is the sheer quality of the ingredients: the taut-skinned and buxom, sweet beef tomatoes in a panzanella salad, the original home for leftovers. They leak sweet juices over your lips and into the golden-brown croutons of fried bread and across huge, breathy basil leaves that are so fragrant they’re practically narcotic. Yours for £8. For an extra quid they’ll throw on salted anchovies and capers, and if you wouldn’t pay up, we’ll never understand each other. There are firm borlotti beans with cherry tomatoes, rings of red onion and flakes of the best kind of tinned tuna.

For those who think these dishes sound just a little too careful and refreshing, there’s the utter abandonment and filth of a fried cheese sandwich, made with thick-cut soft white bread and a mellow cheese that falls in strings down your chin. On the side, there are curls of pickled fennel in an attempt to pretend this plateful might be good for you and a thick, sweet chilli sauce to dip it all into if the mood strikes, which it does. It’s the sort of thing you could imagine eating in bed after midnight, drunk, because you’re an adult and can do these things.

Robust tubes of rigatoni are listed as coming with lamb and celery. The two ingredients have clearly spent a long time in each other’s company, until they know not where one ends and the other begins. It is a butch ragu that demands to be chased around the bowl with every last piece of parmesan-draped pasta.

For the mains, there is a grilled pork collar steak, served slightly pink, alongside a dollop of braised lentils and a muscular salad of flat-leaf parsley and mint. But the star is a whole spatchcocked chicken for £35. It has been half boned out, then grilled with a generous squirt of lemon juice. The skin is crisp and slightly sticky, the meat soft. It comes with a deep, wintery bowl of chick peas and chard, and deep-fried Jersey Royals, bursting from their skins in ragged, golden blooms. It is one of those meals that leaves you mouthing platitudes about the simple things done well. But that’s what this is: the good stuff to which better things have happened.

The closest they get to innovation is a slice of melon, still on the rind, dressed with peppery olive oil and a few crystals of salt against its brim-full sweetness. It didn’t send me home thinking olive oil and salt are exactly what my melon needs in future, but it was fun. A light-textured milk chocolate pot came with a dollop of thick caramel at the bottom and I’m never going to say no to that. We did not drink; it was too hot. But there is a short, well-priced, entirely Italian wine list.

After, we wander the vintage market that occupies the rest of this fractured red-brick estate, resisting the temptation to buy bits of cheap 60s furniture we don’t need, and marvel at the way inner-city spaces such as this can become places that people want to go to. In some ways, Forza Win, with its excellent menu of Italian classics, is following a safe course; but in many other ways it’s an exceptionally brave venture indeed. We need much more of this, if we are to vanquish the bland.

News bites

Hill & Szrok on Broadway Market in Hackney, east London, is another restaurant in an unlikely environment. By day it’s a butcher’s shop. By night, they cook the meat they were selling earlier. Come for veal tartare with anchovy, pork rillette with pickles or a very simple list of grilled cuts from a pork chop for a tenner, through to an 850g côte de boeuf (hillandszrok.co.uk).

BBC2 has commissioned a second series of Million Pound Menu, the business show that saw restaurant hopefuls competing for the investment needed to open the establishment of their dreams. If you have a restaurant idea – perhaps you’re a street-food operator looking to settle down – they want to hear from you. Applications must be in by 17 August (millionpoundmenu.com).

Sacha Lord, Manchester’s newly appointed ‘night tsar’, is holding a consultation on 2 August, looking at experiences of tipping and service charges. Lord says he’s responding to reports of poor practices. The event will be at the Deaf Institute on Grosvenor Street.

Email Jay at jay.rayner@observer.co.uk or follow him on Twitter @jayrayner1