firstly, thanks for answer all!
Superjaggy - tough choice, so agree, according to rank tables Boroughmuir, is consistently rated higher than Gillespies for academic achievement.
yikesanotherbooboo- again so agree, both obviously do provide the resources for a motivated child, from my google research, Boroughmuir is consistently out performing Gillespies, quite significantly. But it doesnt mean my son's academic achievement or performance will be directly effected by that percentage. am quite certain that it does at least play an influence though.
LizzieMacQueen - hehe, yep, its not just the cost, but sheer hassle of moving. actually flat we stay in just now is comfortable, has a garage, something unlikely to get if we move into the Boroughmuir catchment area.