Divide as advised above. I wouldn't wait till end of March either. It'll be clear by end of Feb if it's going to flower or not and you'll just be giving it an extra month of being cramped and starved. In the meantime, try giving it a liquid feed of rose or tomato feed to see if that helps.
Okay obelixx, end of Feb it is, then
Just replaced top 2inches of soil with compost.