Got some niggles sorted on my 2002 4.4 recently - Thought I would share and hopefully help some others with similar issues.
Dropped car off for a general service including spark plugs, oil, filters etc. I also asked to sort noisy starter as although doing the job it was getting embarrassing! My trusted mechanic is great and suggested that he would simply oil/grease up starter rather than replace - I wasn't convinced but let him try.
Got car back all serviced, starter greased up but not really any different. Mechanic apologised for this and said that I was probably right that at 102k miles a replacement due. Anyway I noted flashing battery light while running so mentioned issue - Car left for further investigation.
Note - My X5 has had a flickering battery light on tickover since purchase - A slight press of the accelerator (est 50 revs) would put this out. The flashing while running though clearly suggested a charging issue.
First port of call was to replace the noisy starter, thinking that disrupting this may have caused a short - Replaced, nice and quiet but still flashing battery light! I suggested FSR as a check - I had one at the ready as heater was intermittently cutting in and out. FSR removed, bypassed - No difference, replaced - heater sorted but battery light still flashing when running.
My mechanic had fully charged battery meanwhile and said that all was back to original with only flickering light on tickover - His thoughts are that battery drained down during service due to doors open, ignition on etc. The alternator works but not fully so struggling to bring a drained battery up but ok if battery charged.
Decision time - I want a totally reliable car so went for a new alternator - I have owned my X5 for 18 months and was advised that the flickering battery light was sign of it not operating at 100% soon after purchase. New alternator ordered and replaced - all sorted with no flickering light on tickover, no flashing light when running and no non-starting issues.
So starts strongly and quietly like a new car, runs well, heater blower operates great and no annoying lights

So here is my advice part - Alternator quote from BMW was £1057! (£146 return on old) so £911. My mechanic uses Dingbro - they were £360ish and wanted return of old. I purchased from www.alternatorsnstarters.co.uk - £193 all in delivered with no return required, this is for the 150amp water cooled unit which is a beast of a part. Well chuffed with that - My mechanic mentioned to Dingbro agent who examined part and advised that it was a good quality unit that they also sell and could not understand how it was sourced so cheaply.
Anyway - I have spent a fair bit but all relative a massive saving on what it could have cost and niggles sorted.