Your Domestic ticket will be Business UK. That will give you lounge access and fast track boarding and should give you fast track security. (There was a thread yesterday debating this but my Business UK ticket give me FT security in October)

At check in there will be a Gold/Silver/Bronze desk and I think this includes Club World and First. To be honest I can't remember the exact wording but you should be able to use this desk, either the screen or pop up display will list the criteria.

Enjoy!