think your question got chopped off. please repeat in reply.

I have a Fiat Punto Evo (2010), they do not come with Spare wheels, and as Fiat want to charge £280 + Tyre for a spare (Alloy), I have been offered a Space saver wheel by a friend. The only problem is..... It is a 14" wheel, and the wheels on the car are 16".

My question is.... would it be possible to fit the 14" with a bigger tyre?

As this is only going to be in case of emergency. I know it is a stupid question, and one with probably an obvious answer, but I hate the thought of travelling without a spare, especially over the Christmas period.

so your sayin the 14 will bolt to your car? the holes match? if so you dont really have to get a different size tire as many american cars come with a spare that is smaller than other tires on car. it's called a space saver donut. however, to preserve the handling characteristics of car, and transmission internal differential gears from undue wear, it should only be used on the NON drive wheels of vehicle. however, an exception can be made if the use is very short lived, as in going immediately to a tire shop to have bad tire fixed/replaced. and on your other point, yes, you could get a 14 tire to match hight/diameter of tires already on car as an extra convenience. there is 1 possible CATCH concerning the 14 wheel as it may not fit over disc brakes? i hope this covers the subject to your satisfaction.