[Hanuman]

As a very quick response, (late night guessing) if the ABS is otherwise fully functioning, I'd say there is a switch fault, or someone may have simply bypassed the switch to overcome a witch fault.

The problem that you have is that the abs should be either fully operational, or the system completely missing for the purposes of the MOT (if I understand the requirements). So whatever you do, you should make the the effort to do it in such a way as to make it easily reversed if required.

I'll dig through my various antes later after another think.