Find another 14" alloy, doesnt have to be the same style if its a spare, and get the same size tyre fitted. The trouble with this is with my ones for example, the spare didnt fit in the space in the boot! Ive had to ditch it for a couple of cans of tyreweld tho. If that ever doesnt work, i've got the RAC to get me home / garage to sort it out
15's will fit with no rubbing with standard ride height. Not sure if this is so with 4 people in the car, but I think it's ok, been a while since I had my K10.
15's will rub with -30mm + lowering with 2 people in the car
To solve rubbing on lowering, roll the rear arches and fit bump stops about half an inch tall.