My advice is before you spend any money to put the facts down in writing to the CAA and get their view on it. My belief is that under JAA two people cannot log time unless they were flying a multi crew aircraft. This will not be the case for you. If you knowingly fly around with another bloke logging time and the CAA found out regardless of whether you were the sole manipulator of the controls etc then I would expect them to be very suspicious of your hours and at best downgrade them.