Driving on the "wrong" side! :-0

Hi folks;
I am in the UK for a month to tour about and visit friends before deciding whether or not to move here.
However, next week I have hired a car to drive to Wales and I'm starting to freak out about driving on the 'wrong' side of the road!
I have driven for over 10 years in Canada and the USA and I do have a manual car, but I'm afraid I'm going to screw up real bad here.
Any advice for quickly adapting to these odd motorways??
Thanks!

All the best!!