Firstly, decide what sort of tomato you want to grow. Cherry varieties get ready before larger types and have a more concentrated flavour. Large varieties such as plum and beefsteak are trickier for beginners.
The RHS (Royal Horticultural Society) list of Award of Garden Merit varieties is a good place to start: Link to list of RHS AGM varieties there is more info about the varieties here Search for AGM plants (select vegetables in the ‘Plant Category’ box and enter ‘tomato’ in the lower box).
Sakura F1 AGM: red cherry - high yield; very bright fruits carried on long trusses; very sweet flavour
Sungold F1 AGM: golden-orange cherry - good yield of attractive round fruit; good flavour
Sweet Million F1 AGM: red cherry - long trusses of sweet fruit; good yield
Tigerella AGM: normal ‘classic’ size - interesting attractive striped fruit with quite good flavour; H2 (can be grown outdoors once risk of frost is over*)
Tumbler F1: early bush variety for baskets & tubs; red cherry-sized fruits with excellent flavour
*I have grown all of the above varieties outdoors in East Anglia.
Did You Know?
British Tomato growers use an army of over 100 million beneficial predatory bugs to help balance glasshouse ecosystems where pests are controlled by predators and so are present at a level below those causing economic damage and thus reducing, to virtually zero, the need to use any pesticides which if they are will be primarily biological in origin.