Aimsmum - sorry to hear this, mt cat has had an operation twice to remove stones from his bladder, once was in London and it cost over £1000 but last time was here in Scotland and it only cost £200 as the vet knew excatly what she was going in for so it was a straight-forward open him up op, we had that decision as well at the time it was operate or put him down if it has been another £1000 we would have got him put down but we managed to get the £200 for him.
As others have said there is special diet food but they have to be on it for life and have no other food at all for it to work (at preventing the stones or crystals coming back) I have another 2 cats and it meant putting them all on special food which is £1 a small tin so that would be £6 a day we worked it out to be about £150 a month which we can't afford so he had the op, he's back with us (put back on all the weight he lost) and is on borrowed time until the next time when we will make the decision again
It's sad when it comes down to money but sometimes it's the harsh reality x