Schwalbe Snow Stud, Continental Tube - Woe is Me

Salsa Semi is the 30mm wide rim you seek, listed at £62.99 here, but considerably more pricey than the WTB for the sake of an extra 2mm. I'd be OK with tyres from 28 to 42 on a rim with an outside width of 28mm, and plenty of people will happily run up to 60-622 Big Apples on such rims.

OK, you've convinced me :-)