For anyone that's interested here is Sony's reply to this situation after contacting them (which was a bit of nightmare tbh). The foreign call centre just couldn't grasp what I was trying to explain I had to record a video.
Thank you for contacting Sony Support.
In regards to your enquiry, please note that the part number for the part number below :
(A-2181-290-A TRIPOD RING ASSY (9145))
Also please note that this part is not available separately from the tripod ring assy and we do not advise to change it yourself as the mount assy needs to be removed first, if you want to change the ring assy. As a result, the lens may be not correctly adjusted and this could result in partial blur.
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Basically the screw and knob I need (as seen on this image, they don't supply separately so it needs this whole part in the image. Does not look too bad I thought & I follow on an enquiry for a cost: its this simple cylindrical metal housing nothing more nothing less afterall.
View attachment 301473
The quotation for repair was the part @ £536 inc VAT yes thats right a 1/5 the cost of the lens on this metal circle with a blood plastic nob !, 2 hours labour @ £78 p/h because its a GM lens then insured postage on top of that
That's about £750 to simply replace a plastic f'in nob and a tiny screw !! That's nearly half price of what I bought the lens for. Not really sure this even warrants a response I just wanted to vent some anger. Might just chuck it down the stairs and see if the home insurance will pay out.