I don’t even think they can do this, I’ve just been thru the contract I agreed to and the excesses are hard written in, it doesn’t refer to see insurance company it actually says £50 etc. On top of that the only provision for increasing relates to increase in money to MB not excess rises.
“in place for all applications placed on or after 1 October”
It’s for new applications, not current applications. Yours is, and will stay, £50 until your next lease.
Prior: SEAT Ateca Xcellence Lux 1.5 TSI DSG MY19, VW Golf GTE PHEV DSG MY23
Current: Hyundai Ioniq 6 Ultimate
Next: we'll see what's available in 2028.