I also had a similar demand from Cheltenham a couple of years back....
You should have filled out some forms detailing hours worked, amounts paid, and the employer's details each time you declared the work when you signed on. Do you have copies of these forms ?
I would suggest writing back to the DWP saying something along the lines of:
Just in case the DWP don't retract their claim (implied or otherwise) of fraud, I'd strongly recommend handing a Subject Access Request in to your local JCP office asking for copies of all forms, emails, and computer records held at the local o