Nothing like a bit of Old School technique & experience Dave is there?
Within sensible limits, they are fine in snow up to, I'd say, if the snow is no deeper than rim depth.
I've driven many miles in both our 5s through the years thus...without winter tyres. I find the open diff Mk1 better with it's narrower tyres, and the auto is actually a boon as you can feed the power in from tickover. If bad, I usually knock out the air to 20PSI, but I keep a plug-in inflator in the boot. The 2002 Sport, with it's Torsen diff (as much use as a chocolate fire guard in snow) and fatter tyres needs a different approach and is very much the last resort.
Since it's remetalling refurb and new alloys, it will not see a road unless dry and salt free anyway.
Snow is not the enemy so much as the inevitable salt and muck (not to mention "other" twit road users) which as we know will dissolve a 5 quicker than an Aspirin in hot water...unless it's hosed off after each trip which in freezing weather is a bind if not impossible...even if they have had some sort of proofing done.
Also, with Mazda paint being what it is, the thought of getting grit blasted from traffic and wheel-arch "blast" leaves me cold...pun intended.
From what I've read, good quality snow tyres turn snow driving into the same league as rain driving on normal tyres. They do transorm the car.