cos lettuce

hi all, am still new to all this but due to bad weather what was left of my little gem has bolted before it got even half size.In a panic i popped some cos seed in a large flower pot in my green house is coming up nicely so 2 questions, do i need to prick them out? and should i put them outside? i didnt want to before all this rain because my other lettuce kept going slimy and horrible.I am desperate for some decent lettuce, june provided the most tasty little gem but since then its been a disaster!!!!its about right that my toms are now turning and have cucumber galore

thanks for advice, think the only reason they have done ok in green house is that we havent had much heat lately , will have to pellet them as loads of slugs about and will pop them out.