90Kw pack good for what miles
Dunno about a retrofit, but I had an MS90D (Performance) My longest single-leg drive was 174.5 miles and used 79% (In May, the recorded data says average temperature was 8.4C which seems chilly for May!, but journey was 06:00 - 09:11 temperature started at 5.5C and climbed to only 9C). Average speed 55 MPH, fair amount on cruise at 80 MPH, whole journey bar a a handful of miles at the start, was motorway.
Car was charged to 100%, completing 5 minutes before departure, Climate was on for 20 minutes before departure (i.e. pre-conditioned from Mains), so I reckon reasonably representative of a UK motorway journey on a chilly day.
Looks like 415 Wh/Mile, and I expect I was pressing on when possible as I was not range-challenged. 10 minutes at "crawl", and a good 40 minutes at a pretty steady 50 which was almost certainly roadworks.
That 79% pro rata's to 220 miles max range. I used to work on a max range of 240 miles, so some allowance for pressing-on and chilly temperature. Anything over 180 miles my habit was to charge to 100% (to allow for torrential rain etc.)