We have invested in Stableite, they are not too cheap but very good, they are very similar to the soft play matting you get in childrens outdoor play areas. Very thick but not too inflexible and come in approx 3ft squares. Easy to fit and cut with a good stanley knife. No complaints at all.
forgot to ask, whats the best type of surface, have been told not to get the bubble top one and also not to get the ones with channels in the top..which is easiest to sweep ? thanks for the replies so far but temporary i need something cheap (ish ) and cheerful as the horse is a filthy beast so definately needs rubber flooring. long term and when i can afford it i will probably get equimats but cant stretch to that at the moment especially when my car isnt sounding to healthy!