I owned a S1 24v H564 GDP in Maroon, one of the 2 press cars, it was my second XM, really nice car, but did just stop whenever it liked, fun on roundabouts; although she did fly through her MOT
Anything can be done, only got to watch all the restoration shows on tele, but to do it justice, IMHO, you should lavish money on that, more than many could or would want to, like my CX rebuild, gonna be about 30k when done.
Fingers crossed for her!!
JJ