I think that’s even more difficult if you’re in London. I think that, because it’s the capital and such a large city, it imports food from all over the country, not just England, so you don’t get as much sense of local as you might in other parts of the UK.
As anywhere, seasonal is the key to good eating. So, for example, lamb, rhubarb, purple sprouting brocolli would be things to look out for in March and should be readily available in restaurants. By way of illustration, we had dinner at a restaurant on Wednesday - it mentioned that the lamb was from the Herdwick breed, which is only raised in one county in the UK, here in the northwest, and the bread had Lancashire cheese baked in to it. Provenance would be the other key, so look out for other descriptions of product - whether Galloway beef, Goosnargh chicken or Gressingham duck - if a restaurant is so committed to its sources, it’s likely to be good.
Seafood is always an oddity here - bearing in mind we’re such a small island (with none of us living more than 70 miles from the coast). My understanding is that much of what is landed in the UK goes for export, whilst the seafood we like to eat here tends to be imported. It is utter madness. Even in coastal restaurants, it’s not always a guarantee that you’d be served locally landed seafood. That said, there are parts of the country, such as the southwest of England or Northern Scotland, where local seafood is rightly a Big Thing.
We have a Hawksmoor in the metro area. It was the first the chain opened outside London. First couple of times we went, it was OK. Next time, it was awful - steak so tough I complained. It was not only comp’d but they also offered a free one next time I went. So, a few weeks later, we went back. Another tough steak. So, we stopped going. That was 2018. But, in Janaury, we decided to give it another try. Food was OK but only OK we’ve no need to go back again.
All that said, I note your usual operating procedure is to go for immigrant cuisine in the form of Indian and Chinese, and avoid white people’s British food. Could be a good call if that’s more to your taste. I certainly like both cuisines and have four Indian (and one Chinese) places on our “regular visit” list. My only advice would be to make sure that you are actually visiting a restaurant run by Indians, rather than one of the very many places which might call themselves Indian but are Bangladeshi owned serving very Anglicised South Asian food.
Can’t advise on the beer as I don’t drink alcohol.