This thread is quite timely for me also.
I travelled all across France last year with my van, literally, packed to the gunnels.
If I'd of had to change a wheel for the spare, I would have made sure it went on the rear axle, (swap rear to front first if front puncture), as this wouldn't cause any problems due the spare being much smaller than the 19,s I have fitted.
I realise now, that there was no way the punctured 19" wheel and tyre would have fitted back in the spare wheel carrier, and I physically could not have squeezed it inside the van.
I now have 2 options if I get a puncture this year. (if there is any European travelling this year).
1. Leave enough space inside the van to take a punctured of 19" wheel. (I tried to see if it would go in the spare wheel space, but with 265/45r19 tyres, the circumference is too big).
2. Buy a set of roof cross bars which take up minimal space inside the van, (could even fit them to roof rails both at the rear), and then strap the punctured 19" wheel to them untill it can be repaired.
What do others consider in this situation?.