Visited London last week and called in Honest Burger near Kings Cross upon arrival, as we were ravenous and I preferred to wait rather than eat the over priced junk on the train!
I had the honest burger and gf had the chicken burger; both came with rosemary fries. I had a homemade lemonade (delicious) and the gf had the homemade mint lemonade (even more delicious, tasted like a non alcoholic mojito!).
The burger came marginally pink, but very juicy. The caramelised onion relish worked really well with the burger and salad and most importantly, it was edible as a burger without disassembly. The chicken burger was a butterflied chicken breast in a bun with mustard mayo.
I really enjoyed it and the whole bill came to £24 or so, which at London prices I don't think is bad at all.
I've not been to many "gourmet" burger places, being from the primitive north, aside from large chains, such things are fairly rare, so only have quality homemade and pub burgers for comparison, but it was a much more pleasant experience than your usual fast food outlet!