You are probably thinking of CTC Aviation, based in Southampton.
They are a TRTO company that run type conversion courses for most of the short haul Boeing/Airbus types. They are not strictly a sim company, although they do have two fixed based sim's of their own. One is a generic MCC trainer, based on a Kingair B200, and the other is a B737-300 used as a systems trainer on type courses. Rumour has it that a fixed base B737-700 sim is is to be delivered later this year.
As for the Britannia link, they have 13 pilots in their jet 'pool' which have gained a 757 rating through them. I believe that Britannia are interviewing these pilots with a view to placing some of them. Nobody knows how many pilots they are looking for.
I hope that answers your question.