I bought these in the end:
Toyo Snowprox S954 SUV 285/45R20 112 V XL
I used them in Switzerland and they were great in the snow and ice.
I’ve put them back on the car this winter too as I do a fair commute. Plus it helps keep my 22s out of the salt on the winter roads.
They aren’t as smooth as the factory wheels though.
I used a company called ecutesting.com
sent mine up to the with a description of what the car was doing and paid £255 for them to rebuild it. Unfortunately they did confirm my ecu was at fault but it was beyond repair and they didn’t have a refurbed replacement in at that point. So they refunded all the money and sent my faulty ecu back. I ended up buying a 2nd hand unit off eBay and through a mate of a mate getting it cloned to mine. I’d definitely recommend giving them a try. They were really helpful and have good reviews
To those who may read this merry Christmas in advance. Update as promised: it was as expected. Water ingress to the shark fin area causing the issue. The dealers garage had my car in for brake change so they investigated themselves and found the water ingress issue. I’d pointed them in that direction that is to the great information found on this and other forums so thanks to everyone who’s experienced this issue and posted about the results in the past. I’m on the way to pick up my car. They’ve ordered the part and I’ll take it back in for a day to install when I get a chance.