Tomato novice

It sounds like they might be too dry, If they are in pots as opposed to Growbags, you need to water them every day - do not let them dry out and feed them with tomerite (tomato food) every two or three days once you have tomatoes formed. Another thing is that tomatoes like a humid atmosphere, and good ventilation, which may be harder to achieve in a conservatory, Goodluck.

Also when flower forms - tap the stem of the plant it help pollination aiding the fruit to set - tap fairly hard or give it a little shake