Our '01, with ~76k miles, has been nearly flawless, with the usual maintenance items...
Your list of things to look at/look out for is pretty good. I would dump brake fluid, trans and diff fluid after you found yours.
There is a litany of other items that can go kaboom, (I have avoided most thus far), and the previous owner(s) maintenance would be worth seeing, as would a thorough PPI by you or a skilled BMW mechanic. But, good car overall.
The trans and clutch have run perfectly, though the shifter is a bit rubbery to hand. Few reports of trans or clutch probs on this board or Xoutpost board.
The first gear ratio is a stump puller, so 2nd gear starts or short shifting are quickly learned. The final drive ratio is high, so cruising speed rpms are considerable, but you don't have the distances in Ireland we do here in the US.
Difficult to exceed that 22, imo. I have done one 23+ tank, on a full day trip, cool autumn, no A/C. Best tank ever was 568 miles, but with the 18s not the current style 132 19s.
My OBC 'average', only reset a couple times in 11 years, reads 20.4, but most of that is highway. I suspect teens around town, and 20-22 highway trips.
Good luck with your hunt...
'01 X5 3.0 Sport, 5 Spd Manual, etc.
'02 VetteVert 6 Spd, Z51 susp.
'10 Hyundai Tucson for the CEO, & 3 Assorted M'Cycles.
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