Si batteries best place to buy them any links

[h2ggv]

As above thanks guys girls

[Speedtouch]

Maplin or CPC/Farnell do them. You need either the AAA Ni-Cd type with solder tags (although you can use normal AAA Ni-Cds, and transfer the tags from your old batteries across), or the later and shorter Lithium type, depending on whether they're Moto-Meter or VDO clocks.

[Brianmoooore]

If the wiki says AAA, then it needs amending! The batteries on the older type board are AA, and CPC BT04108 are the closest you'll find - OE make, but the tags won't fit the board directly, so short pieces of stiff wire are needed.
CPC BT05108 if you need the lithium type for the later boards.
Note that CPC no longer charge exorbitant rates for carriage on small orders.
Board types are not VDO or Metermech dependant, but are early and late versions. All original NiCd boards will almost certainly have been replaced at least once by now, and it was random whether your replacement from BMW was a new lithium board or a rebuilt NiCad board.