Thanks everyone - the support really helps and especially the positive stories.
Sidge - they haven't told us where yet but from the reading I've done so far I reckon it'll probably be Glasgow Yorkhill.
Saggar - it's a ventrical septal defect but towards the top of the v-shaped fascia - so in the thin bit, not the thick bit at the bottom, which is why they reckon it's not likely to close over itself as he grows.
The cardiologist said last time he wished it were either smaller or bigger than it is - if it were smaller he'd just have told us to go home and not worry about it any more as Moomintroll would be fine, if bigger the surgery would be a far more clear cut decision.
As it is he could go on to live with it without any problems but it is already affecting his feeding - he pants and sweats a lot and can't take more than 140ml max at a feed, so feeds about twice as often as his peers, which is pretty tiring for us and for him I guess.
He's an absolute wee trouper and has already sailed thru' surgery for a hernia at 10 wks - they even let him home the same day which is very unusual. He's v strong, has a great sense of humour and holds nothing against anyone, all of which I know puts him in an excellent position to come thru' this really well. In a strange way tho', that's why my heart's breaking for him - it's not about fair or unfair, these things just happen, but somehow it all seems such an abuse of his good nature. I know it's for the best, it's good that he'll be young enough not to remember etc. etc. and I'm probably not making any sense but I just wish I could take this burden off his wee shoulders.
Anyway, thanks again for the support, info and hugs - all very gratefully received.