Self employed van courier?

[slappy]

Is anyone on here a self employed van courier or has been one?
Reason for asking my son got put on short time by his shitty employers and has been offered a self employed position as van courier with UKmail.
He will lease a van from Hertz and has been given a route in Wetherby and is all set up to start.
He does realise that it won`t be easy at first and he will  be working more hours than he has ever done before but the only other jobs that are available are minimum wage and even they are few and far between.
I have a few questions!!!!!
When should he tell the tax people he is now self employed?
We think his best option is to get an accountant to do his tax/expenses stuff, if he gets one will the accountant inform HMRC that he is self employed?
What can he claim as expenses if he does not use an accountant?
Does he get tax relief or similiar on fuel he uses and the van lease?
Does he need liability insurance for the goods in transit?
Does he need to tell his mortgage lender he is now self employed?


Any help or guidance would be appreciated.