Clockwise from top left, you have: Spring Tree (cherry); Summer Tree (orange); Autumn Tree a (oak) nd Winter Tree (fir). Each print costs £15 (small, 175mm x 235mm) or £30 (large, 297mm x 420mm) and they come unframed.
The small sizes are thin on the ground I'm afraid, as the limited edition prints went on sale a while back – and I only just spotted them while browsing the online store because it currently has a temporary closing down sale on (25% off many nice things... just so you know, while they revamp the shop). But large sizes are still plentiful.
Or if you can't stretch to a set of full-size prints – they also have postcard packs; a set of eight for £9, based on the same designs. Send four, and you still have a full set to frame.