Having spoken to Apple about the expose lag problem, they suggested the following to try and remedy the problem:
1) Repair disk permissions
2) Create a new account (preference related problem)
3) Erase and install OS X
Unfortunately none of the above helped and the lag persisted.
The technical advisor said if the erase and install did not fix the lag problem, it is not software related, and therefore, must be due to faulty hardware.
Apple have acknowledged the problem and a replacement will be issued.
I agree with the previous post - that drivers may indeed be part of the problem - but at £1600 I cannot afford to wait and see. Will soon find out upon receipt of new MBP.