'Screwfix' cable suspended D92502-79 GU5.3 20w 12v halogens [5 off per set] @ £37.99. 5 spots per string.
View here: http://www.screwfix.com/app/sfd/cat/pro.jsp?id=92502
Adjustable Spots model D16071-79, similar @ £59.99 with 5 off 35W x 12v spots, 5m span.
They are indeed fast and efficient. If it's in the catalog, it's in stock, and I've ordered at 6 or 7 p.m. one day and had it delivered next afternoon. Probably going to be a little slower to the IoM though.
Looking in the current BDC catalog at Micromark lighting (all exc. VAT):240-volt:
MM31481 2m white track, £11.09 (5+)
MM31487 Universal spot 100W R80 or Par38, £4.03 ea. (5+)
MM31488 Spotlight, Par20 or R63, 60W, £3.94 ea. (5+)
MM31489 Spotlight, Par30 or R80, 100W, £4.38 ea. (5+)
GU10 spots avilable at around £6 to £7 each.
Not sure about delivery to IoM though. Nearest depot appears to be Manchester, which is also the main export office.