Yeah a grinder was an option but I like a challenge so loads of WD 40 over the pst week and a new 18mm socket, all off now although one of the legs of one of the U bolts did shear as soon as I put any pressure on the nut to undo it.
I will be replacing the U bolts and all of the shackle bolts etc.
Out of interest I am assuming all bolts etc are as a standard SIII, hope so that is what I have ordered? (not springs, I have used, v. good nick ones from a lightweight after someone changed to parrots rubbish.