What is your budget and in which areas? Anything you don’t want to eat? Anything you really want to try?
London has a huge restaurant “scene” so you could get 100 recommendations and still not even start! :-)
As a start have look at some restaurant review sites. TimeOut London and Hot Dinners are both good places to start.
From this locals point of view
Indian- Dishoom, Roti Chai, Darjeeling Express, Masala Zone. If you have money to burn Cinnamon Club, Gymkana, Kricket
French(ish)- Brasserie Zedel, The Ivy, The Wolseley
Noodles- Shoryu Ramen
Chinese ( Szechuan) Baozi Inn
Meat- Blacklock, Flat Iron, Hawks moor, Montys Deli
Italian but more regional- Polpo, Tozi.
Lunches-Pret a Manger, Eat, Marks and Spencer food halls/supermarkets for prepared sandwiches and meal deals. Waitrose and Tesco also do good deals.
Don’t have fish and chips in a pub!