DOES ANY ONE KNOW WHERE I CAN GET DRY DOG FOOD THAT HELPS PREVENT STRUVITE CRYSTALS? DONT TELL ME TO GO TO MY VETS THEY CHARGE A VERY LARGE SUM OF MONEY, WAS HOPING TO FIND SOMEWHERE IN THE UK ON THE INTERNET. PLEASE HELP ME  :-)

Have a look at this site it would appear that a prescription diet is necessary to break the crystals down, I don't know of any substitute, expensive it may be but I think you have to think of it in terms of medicine.  If you have any insurance they should cover this I would say.  The site seems to be suggesting that the real issue is infection and regular monitoring is the key to prevent the crystals forming by ensuring antibiotics are used sooner rather than later, perhaps you could discuss how you could achieve this but I would think one way is to buy testing strips from the chemist and check for proteins in the urine which usually signify an infection.

Struvite dissolving diets are prescription only diets.
The point about antibiotics is correct, an infection often predisposes the dog to struvite formation - has your vet done a urine culture?