Mercalot, you did the right thing. I'm in the south, and I know a Merc dealership that offered £990 fully fitted for a set of Continental WinterContact 810s on a set of 18 inch wheels. The price is probably 20-30% higher on 19 inch rims (Continental don't do these, as far as I know, so you're at the mercy of others if Vredestein aren't available, which is the case now).
Depending on your exact spec, you're in the right price range (I suspect you've big wheels for the rear).
Driving in London when the recent freeze occurred was instructive again on 225/45/17 shod summer tyres. A 10 minute journey took 45 minutes. My new Conti Winter tyres arrived this week and will be fitted tomorrow, in time for the weekend's freeze. They'll cost me all of £650 fitted, but that's because of how and where I bought them and who will fit them. There was no stock left in the UK (one outlet had seen a 25 fold increase in demand this year on last year - that tells me a lot), so I bought elsewhere.
Our priority is to be able to get moving if we need to. I'd simply ignore the sceptics on here if I were you. You'll be able to make emergency trips to the GP, hospital, pharmacy, refuel, and supermarkets whilst others around you are trying to get traction off their drives, parking lots, or slight inclines.
Germany mandates winter tyres in winter, and has many more Mercs on their roads than in the UK. There's nothing wrong with your having bought a powerful new car with wide wheels and summer tyres. As far as I know, even if you tried to, you couldn't spec a UK car to be shod with winter tyres at the factory.
So the word is out in the UK on winter tyres. I'd never used them previously as I am usually in Southern Europe for the winter. However, this winter promises to be special, and if you've seen the forecast for the coming week, your £1,000 outlay will repay you yet again, and that's before the economics which have been so well demonstrated by someone else on here.