Think i've found the problem.

The inside of the boss they got me starts getting smaller (gets thinner one end) straight away where as on my old boss it's a normal hex for the first bit of the boss then its just a normal tube to go around the threaded part.

This means the new boss doesnt even try to go on!

Starting to get annoyed with it now. Asked for an MK3 escort boss, took 5 weeks or so for this one to reach me and it doesnt fit! I think im going to end up trying to drill holes and modify the original boss