I will be switching to winter tyres on 19" wheels in coming weeks but I've only got a set of 4, no spare. My current spare is a full size 20". Is anyone able to guide me whether it would be OK to keep the same spare wheel for short term emergency use or running on one 20" wheel with three 19" ones (in case I get a flat and have to use the spare for a bit) is a bad idea and I should get the correct sized spare?

Thanks

You can use a 19" emergency spare with 20" so why not vice versa provided you treat it as an emergency spare in relation to speed etc - I cant see a problem  Wanted a Series 2 LR since childhood but previously owned MY16 Disco Sport HSE TD4 Auto, MY13 RR Sport Black Edition TDV6 Auto, MY10 RR Sport HSE TDV6 Auto, 2007 Freelander 1 Freestyle TD4 Soft Top, 2009 Freelander 2 GS TD4 Auto, 2007 Freelander 2 GS TD4, 2004 Disco 2 Metropolis Auto, 2002 Disco 2 GS, 2000 Freelander 1 SE TD4 SW

Still hoping for a S2 one day!

Yes, I also thought about 3x20" + 1x19" being fine. Just want to make sure there are no issues when that is inverted, so I can stop worrying about it.