Hi Brian and welcome.
I've have a high mileage 2011 XF (pre upgrade). Apart from getting the gearbox oil changed as soon as I bought it (there was no mention of it in the service history), I've had no real problems with it, it's passed the MOT every time with no problems, a service at the time is the only time it's been in a garage. I had a problem with the fuel gauge, which, told in another post, took me a Youtube video and about 45 minutes to fix, a fob battery warning which turned out to be the battery on th spare fob, and a thermostat leak which luckily happened during a service so was repaired at cost. Going by my car only, I can only whole heartily recommend it. I hope this helps.
Regards
Phil