What ho one and all,

I will be renewing the manual transmission oil in due course but first, needed to check that I can undo the fill nut. The answer if yes.
While under the car, I am gradually releasing any bolts, nuts and those small panel clamps. applying copper slip and hopefully, they will be fine for any future access.
But nothing goes according to plan and a few of the bolts with the captive nut clips are rotating. I will have to drill them out and replace. So I need some of these but don't know what they are usually called for a Google search or what size.



This is the bolt the rotates; what size are they? It takes an M8 or sometimes M10 socket but that is not the actual thread size.



Grateful for your advice; many thanks