Thanks figrat and Alina W .
Ahhhh - yep, the radiators are on in the room and the tray is on the floor so they probably are reaching for light.
Sorry, I'm not great at the techncial lingo yet so rather than bolting they are just 'leggy'! I'm learning so much... also to label seeds (which I failed to do)!! I got so carried away, and thought I'd remember everything that I planted, only to completley forget when they starter to come up! Definately sweat peas, tomatoes and corriander though, and some flowers called 'lace caps' (which are more leggy than than a group of super models in 6" heels)! I planted them a couple of months ago.