Well i used a local supplier called woody pets who were very reasonable IMO, it was £250 for delivery and fitting of 6 6x4foot mats which i think is generally rather good, and they are very good quality and have a 10year guarantee on them.
Cow matting is supposed to be very good and is much cheaper than the stuff labelled 'horse matting' and you should be able to get that at your local country store
Don't know if "cheap" & "good quality" necessary go together. Our mats are Aquamats (www.aquamax.co.uk) and there is a local agent to you in Suffolk. Ours have been down for almost 4 years and have never needed lifting and show no signs of wear. If you are planning to move in the future and need to take the mats with you, you might be better off thinking of equimats which are much lighter than traditional matting and easier to move.
I have purchased mats off ebay via seller - midland mats supplies and have been very pleased with them, my friend who has 5 horses had bought more expensive mats for two of her stables but has now kitted the other 3 out with these and she prefers them to the more expensive ones. Hope this helps!
Someone I met the other day said they bought their rubber matting really cheap from the Local Council. Apparently they rip up the rubber matting put down in play areas every few years and sell it off. Might be worth a call to your local Council.