Hi Everyone,
Apologises for the delay... I only got to this earlier this morning... The good news is the part referenced above fitted perfectly and after a couple of hours of "f-ing and jeffing" I managed to replace the part.
A quick trip down the MOT station and I'm pleased to say it passed! So for all the Superspec owners out there, hopefully that is another part number identified!
At least with my MOT now being in the middle of the season I might actually get out a bit more early season next year!
Thank you to everyone for your input and offers of help.
Matthew