No belt on that heap of an engine

I have a TD, and if I can give you 1 piece of advice:
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CHANGE THE OIL EVERY 3k MAX[/size]
No messing.
The timing chain is lubricated by the engine oil, obviously. Diesels use the engine oil to carry away particulates caused by the diesel combustion process (thats why diesel oil changes are more frequent, forgetting marketing BS). This makes the oil 'gritty' which accelerates wear on the chains and spockets. Officially, to change the chains and spockets on this engine is a cylinder head off and sump off (later probably means engine removal from car), so not a job you want to do. When the chains wear, they tend to jump a tooth on the spockets. This also (officially) is a head and sump off job.
I know BMW raised the service interval from 4.5k to 7.5k, but this was for marketing. Even 4.5k is too long for this engine. If they car has not had recent 3k oil changes, do some 1k oil changes for a while, then back up to 3k.
Longer life oil will not help, as the oil needs changing due to the particulates, rather than oil breakdown.
Please, please, please heed my advice.
(Vx semi synth is around £32 for 20l on trade club, and the filter (yours will be cheaper later type) is around £6 on TC. You will need a 36mm socket for the filter as well. Also, then sump plug is prone to stripping, if yours is M12 one, double check with dealer on torque setting - I think its around 20Nm.