After a lot of investigation, I decided to buy a very good used passenger seat and ask a trimming to use the perfect bolster to repair my tired driver's seat.
The seat is perfect. Seriously, totally back to as-new condition. Will get an image here soon.
So a big shout out to RJ Turner in Sevenoaks whose rate was extremely good in my opinion.
Also, if anyone wants a passenger seat with perfect tartan (but no right hand grey bolster!), let me know.