Wotcha and welcome Gaz - Bazza (Barry) had a bargain classic located not too far from you (Canterbury Kent) dont know if he still has it though...??
give him a ring on 0771719545
http://uk.subaruownersclub.com/forums/topic/8888-bargain-bagain-bargain-dont-miss/
parts prices will be comparable to your MX5 you can by budget stuff or higher end, yes a service every 5k is a good idea with cam belt and pulleys looked at 30K (im more cautious others will leave the belts longer)
dimensions are Wheelbase 2,520 mm (99.2 in) Length 4,340 mm (170.9 in) Width 1,690 mm (66.5 in) Height 1,405 mm (55.3 in) Curb weight 1,220 kg (2,689.6 lb)