Hi guys. My car did not come with a spare wheel (Bought it 2nd hand) but a foam spray can.
I am going on a long journey next week and don't feel comfortable with just having a can of foam.

I phoned Audi and asked how much an alloy wheel would cost me. An 18" S-Line 5 Spoke alloy is £484.00 .. plus the cost of decent tyre which is £200 totalling £684

Now my question is..instead of having the proper alloy wheel attached to the spare tyre can I just have no alloy wheel and just a spare tyre?
If I get a puncture I can put the spare on and get to a garage who will put the spare on the alloy or something..Will the AA put the spare wheel onto an alloy or just put the spare tyre on?
Is the spare tyre 'full-sized' 18" ? Or what size is it?

What tyre do you recommend having as a spare? Same as the ones I have at the moment?

Thanks.