Altering language combination of a TM

I am having trouble using one of my TMs in Studio 2011 due to the fact that the language combination is set as Spanish - English (US) rather than Spanish - English (UK). When I translate in Studio it is generally into UK english but when I set this language combination for the document then it does not allow me to use my TM as it says the language combination does not match. I didn't actually intend for my TM to be marked as US English so is there any way that I can change it to UK so this doesn't occur again?

Thanks

Katharine