A quick look at mytyres dot co dot uk shows £70 (avoid) to £323 (gulp) in that size and speed rating! They show test results for most of the tyres that include wet, dry and snow performance, comfort, noise and wear so you can weigh up what is important to you.

I can recommend the Vredestein Wintrac Xtreme which is mid price but scores very well especially in snow grip and overall as well as the tyres costing £100 more each. Prices not surprisingly seem to have gone up quite a bit in the last two months. There's a mix of winter tyres on flea bay in that size. Whatever you buy, you'll need to check you've got the right load rating which I guess will be higher due to the weight of the van.