185/55/15 - £51.92+VAT per tyre in the Yokos
These are not studded, you cant use studded tyres on the road here, which there's thick snow you're fine, but as soon as you hit the black stuff again not only will they get trashed, but if you get spotted with them you'll get in a spot of bother
Those 20" sizes Yokohama dont do, and if somebody does them, they're likely to cost a small fortune Perhaps look at some cheap 17s - maybe standard wheels, and chuck some winter tyres on those to save your 20s from ruination?