I appreciate the replies but after further investigation it seems the Ebay pumps kits are not the same pump as the 130i. Mine as an ATE pump while the 4 cylinders appear to be Bosch or something along those lines. It does indeed appear to be a case of the brushes wearing down to failure and that would fit with the fact that it happened very rarely to start with, then more frequently and now permanently.
The Ebay listing is also for E81, although in theory that would be the same as E87.
Have currently got two options. Burger motors said they can remove the unit and send to Tauranga for repair at a "reasonable" cost, otherwise I can pull the unit and send to ecutesting.com in the UK for repair at ~200 pounds.
Mildy miffed at the price BMW are charging :/ Oh well, the car hasn't had any other faults in the last 2 years so it's not all doom and gloom.