Hello Peblig Community Garden Project,
In colder conditions, there are still a wide variety of crops you can grow. Potatoes, cabbages, root veg and lettuces should all thrive. On seed packets you will see a range of times for sowing outside. Avoid the earliest times to be on the safe side. However you can also use cloches and fleece to protect your sowings and young plants until you're sure that the frosts are over.
Pippa's written a blog in favour of fleece:
and there's a project on making your own cloches in our How To section:
Do let us know how you get on.