Ok, sorry for the late reply on this one. Actually forgot i"d posted it! Dumbass!
Anyway, thanks for all the replies. Here"s my thoughts:
The reason for the call pre-flop was that i"d put him on a medium pair given his previous play. But it figured if i 3 bet he would be happy to shove and i wouldn"t be able to call. However, if i hit the flop or it comes with high cards i can win it as he"s not calling unless he hits his set, given the way he"s played so far. My biggest mistake here imo is not taking into account the stack size of the big blind behind me and what he might do. I soon realised this when he shoved, hence why i was ready to muck when the original raiser re-shoves. Once he turns over his hand i have a decision to make.
My reasoning here was that i still have a good sized stack if i lose but if i win i have a great stack at this stage and if i win the side pot i pick up chips too so i called. I was happy to take a bit of a gamble as i was getting decent odds and the advantage of having a big stack against the people who play in these is huge.
So, what happened. Well, the BB turned over Queens. Not so good but i"d seen him shove with a LOT less.
Flop A-x-x. Happy days!
Turn - Queen - Ouch
River - Eight - FML
Don"t mind my call here so wasn"t too bothered but was intrigued to see what others would do. And if it wasn"t for the Pokerstars special on the turn and river i may be on here telling you i"d won the whole thing!