Hello Paul,
Haha! That’s what curiosity, a polytunnel and an over-eager attitude got me started!
The tomato plant must (am using this word rather cautiously) never be wet. That is, the leaves and stems mustn’t be wet or splashed with water. When we didn’t have our polytunnel in the first year, I still wanted to grow some tomatoes and they were grown outdoors. They fruited beautifully, however that year got rather wet and rainy. And as a result, the leaves and fruit and stem turned brown and black and eventually the plant just got killed off. Many people I know too have this problem when their tomato plants aren’t grown under cover. Keep the stems, leaves and fruit off water!
The tomatoes I recommended tend to gear towards the sweet side, some not overly sweet. (Btw, my husband’s favourite tomato too is Sungold! It is predominantly everyone’s favourite! However, I still love to experiment and try new varieties.) We also have another tomato house only about 1.5m tall (compared to our 3m tall polytunnel) and I will be experimenting this year by letting the side shoots of the tomato plants grow.
Have a look at this too:
http://savvygardening.com/five-questions-with-tomato-expert-craig-lehoullier/
ps: spelling error for one of the tomato variety … it should be Omars Lebanese