Got your pm but can't reply on iPhone - have a mobile number will send it to you tomorrow though can't remember his name! Other one to try is fishlock stables he does arenas too, number is 01945 701131 (Gary fisher - tell him Ian and Abby recommended him!)
We used :
Mallow Arenas
Walnut Tree Farm
Ely
Prickwellow Rd
Cambridgeshire
CB7 5RG
Phone Number: 01638781794
6 years ago now - excellent arena - never puddles apart from during a proper downpour and is gone within 30 mins.
We bought from stud 10% deposit, they paid routine vet/accidents etc until collection plus foot trims and feed - option to have deposit returned in case of accident/injury affecting value
Yes, did it ourselves for cost of new chassis, new u bolts and meal for friends who had loadall and a forklift - sold old Bedford chassis and that paid for box refurb - have a very handy OH though