Thanks guys! I've had her in the freezer for 24 hours, will find some oil and give it a crack - I might have some around here, I don't use it for cooking, but I do have some stretch mark and baby oil samples from baby expo yesterday, not their intended use, but might work? Otherwise I might have to pick some up.
Edit: She's almost done! I happened across some hair oil (Garnier Miracle Oil in case anyone has the same issue) in my bathroom cabinet and used that - it worked perfectly - the freezer did nothing to the blu-tack, it was exactly the same! The oil just melted it though, which was great, and I just combed it out. The problem now is that I need a finer comb, as there are still teensy bits in there... the one from my pony kit seem to have gone walkabout, so I'll have to pick up a new one tomorrow.