The technique for growing tomato on an allotment is virtually identical to growing them at home. Some varieties are indoor and some are outdoor. They can grow successfully from seed, but if they don’t then cheat and buy them from a plant sale (most allotment sites will have plant sales early in the season). Like anything in growing, don’t assume that because you didn’t get any plants from seed last year that you won’t again this. Plants are fickle, seasons are fickle and despite what the experts will tell you a lot of it is down to chance (though doing the right things can reduce the element of chance involved).
If you dig manure into your greenhouse beds in the autumn it will be nicely broken down come the time you want to plant your tomatoes. You will also need a good supply of tomato feed once the fruit are showing.
If you are growing taller or vine varieties then as the plant grows squeeze out the side shoots otherwise you will get all plant and non fruit. Make sure you support the plant below each truss of flowers (later fruit) so that your fruit don’t pull the plant over when they are grown.
Keep the greenhouse well watered and plant some marigolds round the base to keep the blackfly off and some basil in pots nearby to keep the greenfly off. If you get a lot of greenfly on the basil take it out of the greenhouse and shake the greenfly off.
A healthy tomato plant will grow to 5 feet (or more) and produce several trusses of fruit. If the last of the fruit are still green as the autumn closes in then hang banana skins near them as this will speed up the ripening.