while the rack is removed I think I will fit a new starter as I don't want to do all this again when this 30 year old bad boy retires.
I have the choice of two one fits one doesn't evidently, early and late dependent on pinion size, early is 29mm late is 25mm engine # b4 and after
engine no 7000. as my engine no. bear's no resemblance to 7000 its 85029145, is it safe to assume its late?

 

Your engine number more than likely begins with 8S not 85. This makes your engine number 29145.

 

thanks for that, your right of cause.
I guess I should have gone to Specsavers,

 

its arrived quicker than the new rack and weight is commensurate with size,
hope the threads are metric assuming BH506271J are.

 

well pleased with the high torque starter, sounds great and hopefully will never let me down in my future, £200 well spent, that's another £400 with the rack, just for the love of working on it,