Pfft men
Use logic, baffles most people
1. Use the 17" for winters, sell the run crap tyres on ebay if they're newish, outlay = new tyres - sold tyres
2. Buy new set of wheels + tyres (you are always going to have to purchase tyres at some point)
3. When you sell the car, take nice wheels off and sell them on ebay.
For me doing so many miles it was an easy sell to myself
1. New winter tyres @ £450.00
2. New wheels & tyres, BBS 18" CK with Goodyear F1 A2 @ £1,200
3. Sell them for £500.00 with remaining tread on tyres (if I get more even better)
4. Cost of RFT for 75,000 miles = 6 tyres @ £150 = £600.00
Thus total extra cost = £450 + £1200 - £500 - £600 = £550