Ill just be running my summer tyres againthey were perfect in the snow last year
Good enough, perfect I'd dispute.
Is there any reason I can't just use my OEM alloys with the correct profile winter tyres, and then have my existing summer tyres refitted ~March ?
In the long run a set of steel wheels will be cheaper as you'll be paying about £80 a year in tyre changes (£10 a wheel a time on average).
Insurance companies should see it as a reduced risk. You are making the effort to use winter tyres, so any suitable wheel should be ok. Hopefully you'll speak to someone who understands.
No UK based stats to back it up in insurance terms yet though unfortunatly.