Hello
dukess1999 I bought a second hand starter motor last year for a 748bp for £20, if indeed this is your problem,
I would ring around some breakers, as the one on ebay is a little over priced.
But I would look at this being your last option, as stated before its not a common fault starter motors packing up, be careful if you do disconnect/connect the nut/wire going into the starter motor as this can damage the wires/connectors internally.
hope you find the problem soon.
regards
TopiToo