Hotpoint eg74?

this was in excellent working order. Sold on ebay 3 days later buyer phoned to say it isn't working. Checked 1 wire was out behind the control unit the oven, top oven and grill don't heat up and the grill on off switch now turn on the cooker light and fan.
Suspect they have either changed the wire around because the price went high and they wanted a refund or changed the timer unit for a faulty timer unit they had.
Any ideas or idealy a picture / diagram of how the wires should look would be great.