Changing URL of WPMU Buddypress site.. Need advice please.

Hi
I am running Buddypress Magazine theme here:
http://www.quickcashgenerator.co.uk/carsite

This is where I have been building the site but the plan is to put it on the domain beds-modified.co.uk.
I have pointed the name servers for beds-modified.co.uk to my server and added it as an addon domain.

Please can someone advise me on the best method to get the site working on beds-modified.co.uk.
I want it to be running on the root of beds-modified.co.uk rather than beds-modified.co.uk/carsite for example.

I know how to search and replace in Mysql but don't want to go into anything too soon without getting your suggestions first.

There is one blog attached to the site and it is domain: quickcashgenerator.co.uk path: /carsite/

Thanks
Andy