Front Upper Arm Shaft MG TF

Hi
Does anyone know if there is any difference in part nos 2A4325 and RBR000020,I know that the first one Metro and MGF is no longer available,replaced by RBR000020.
I have managed to find a new old stock upper arm for £55 plus postage,and want to use an original shaft pin if possible .
On Ebay there is ex factory stock shaft pins listed as both part nos for less than a tenner.(but not clear on which one)
I plan to use the collar and spacer from an aftermarket kit that I had used a few months ago,but play has returned .This may be because I had to dremel one bearing case out,which caused a grove in the housing that I filled ,as the new arm was so cheap it seemed the best way to go.
I don't want to pay Rimmer Bros prices for a genuine shaft or bearing kit. (£114 for kit or £63 for shaft) I don,t mind spending £12 on original coller and spacer if this is the best way to go.
Are all aftermarket shaft kits produced to the same dimensions ie. shaft diameter and collar sizes , as I could purchase one from Rimmers,and not change the bearings but use the shaft and collars.
Has anyone used an after market pin in original bearings ?
As I have spent so much on the car,I am looking to make the most cost effective long term repair(plus its a pig of a job) just to undo five bolts! I don't want to have a third attempt.:rant: :rant: :rant: :rant:
Any expert advice on which way to go would be appreciated.