... I've just phoned and apparently they have no record of a request ???? Fortunately the call was a 3 way hookup from orange which was recorded...
Perhaps you can prove from your phone bill that a call to Plusnet took place?
Regarding the "3 way hookup from Orange", that is a slightly strange non-standard way to obtain your MAC. I speculate that may have contributed to the "poor record keeping". In any event, while many ISPs provide a MAC during a phone call, that's not a regulatory requirement.
Plusnet operate a very good "ticket" system. In my experience any request made becomes a ticket. If that did not happen certainly something went wrong.
And according to the ads Plusnet call centre staff are all based in Sheffield, England.