ah if its lined mate i make you right, all you'd have to do is step on one jagged stone and you could be in trouble

Fill the swimming pool with water from the pond, and throw your pump in there and at least you'll still have the bulk of the bacteria you've built up.

Good luck with it mate, I know it'll be hassle but when it's all done and you can sit back with a few beers and have it just how you want it, it'll be happy days Phil