Hi there,
Thanks for the response. My car does not lose power altogether it happens intermittently that as I set off the car will move, the revs build up but I am only just rolling. However, as I am rolling the speed increases and catches up. This can go on for a while and then all of a sudden it reverts to driving absolutely normally and can stay that way for many days and then it happens again. After having a discussion with my garage, (who is a Jag specialist) I told him that I thought it was a problem with the communication between the potentiometers at the accelerator and the throttle body, He initially was reluctant to accept this, but, after discussing it with the dealer I got the car from. he had another customer with the same problem some time ago and replacing the throttle body body solved it. So, the dealer has now arranged with the garage to replace the throttle body on my car (no charge) which is being done Wednesday and will hopefully resolve the problem. Will post again after I have driven for a while.
Cheers.