It's a valid point. I'll counter that by saying that riding a nice bike is more enjoyable and motivating that riding one that isn't, for me at least. If having a 'nice' winter bike means actually riding it rather than being put off by having to ride a bike that feels a bit crap then that's probably worthwhile.
Besides, I find that if you stick with fairly cheap cassettes and chainrings then the cost of wear and tear is pretty minimal.
AND... (Without spending the OP's money for him)
As you're buying a bike on the C2W scheme, you're saving a lot of money anyway... You could buy an buy an uber cheap bike yeah, or you could buy a nice one (still with clearance for guards) that as clubber says, you will want to ride more as it's more enjoyable. Properly maintained, all you should be wearing out is the usual consumables anyway, and then when spring comes, treat the bike to a full service, new cables and some new (faster, lighter) tyres and take the guards off, and you'll want to ride it through the summer too!