When Hugh-Fearnley Whittingstall did his taste test the winners were Sungold, Santa, Brandywine, Nectar and Odoriko.
Sungold, Brandywine and Santa are available from Thompson and Morgan. Simpsons sell Nectar.
I'm not sure about Odoriko. If anyone comes across it, I'd be grateful to know where I can get seed. I DL'd the RHS veg. seed suppliers' list and they DO list it, and say there is one UK seed supplier in 2012, but for some reason that's all the information you get! Further Google searches have been fruitless - literally!
I've grown Sungold and Brandywine in previous years and can definitely recommend them for flavour.
This year I'm growing red, yellow and black cherry tomatoes only. I can't tell you what variety they are because I sowed them from seed I saved from a supermarket punnet!