cucumbers to cloche or not

Sulking in what way?  Yellow, leaves drooped, spindly or no growth?  And presumably they are outdoor types?

At this time of year (and recent warm spell) they should be moving along - a cloche shouldn't really be necessary unless they have got a bit whiplashed in the wind?  Maybe they need a liquid feed to give them a boost?  Cucumbers like their squash cousins prefer very fertile soil.  Another possibility is that the roots got pot bound and when that happens, the root ball tends to stay small and then they can stop growing because they are unable to take in sufficient water during warm weather or nutrients for growth.

I put a bit of fleece around the frame on my outdoor plants just too keep the wind off and touch wood they've taken to outside life