mikehugescq

I grant you that malicious intent may not be relevant in this case as the investigators have followed the poor fellow for 5 days already without asking him for an informal meeting.
At the first point of contact with the fraud department the malicious intent of the informant is very relevant and it is important to point that out to the investigator.
Most people know or have a very good idea of who has reported them.
The fraud department gets many untrue malicious allegations against people and they do not have the time to run around investigating false malicious allegations.
The malicious intent of the informer can play a large part or can tip the balance as to whether to drop the investigation or to continue.

For example: If you are having a feud with an antisocial neighbour and trying to have them evicted. it is important for the investigator to know this.
It makes the informants report and evidence of your mobility suspect as well as their motive for reporting the alleged infraction.

I object to you referring to other peoples advice as "tosh".
At the time of writing we did not know that he was not receiving enhanced mobility.

The time for a solicitor was at the time of the interview under caution in this case.

The mans PIP has been stopped and he has been followed for 5 days by investigators . He has had an interview under caution.
To do that the department has spent considerable resources which it is short of.

I would be taking this seriously and talking with a good solicitor so he is up to date and ready for any summons that comes.

Get a benefits adviser on the case and find out why all your benefits have stopped. 
From what you have said you have cooperated so they need a reason for stopping your money.
This might put a little more light on the situation.