the enforcement agents, in theory can’t take any possessions from my mums as we do not have anything of ours there.
And they'll take your mum's word for this?
I think we’ll just have to wait it out and see what happens
Really? For the sake of a few pounds of tel. calls you're prepared to potentially have her subjected to bailiff action. Oh well.
IMO, pay the bailiffs. If they'll accept the pre-£235 sum good.
This gets your mother off the hook.
Then in a slow, measured fashion you can set about finding out what's what. And after you've submitted a Subject Access Request(SAR) to DART you'll have all the documents and can submit your OOT to TEC.
Paying the bailiffs has NO effect on TEC's final decision and essentially if they accept your reasons for submitting your SD late and revoke the Order for Recovery you get your money back.
SAR - is a data protection issue, nothing to do with traffic contraventions as such. They're required to provide you with the personal info you request which in this case would be all their correspondence, including the initial PCN.