I'm not completely sure, but I think that Bret's Work Permit was[/u] his entry clearance. Cole & I had to fill out paperwork (Dependant of Work Permit Holders) and send it, plus our passports, extra photos, $$$, birth certs., marriage cert., etc. to the British Consulate (NYC). We received our passports back with our Entry Clearance stamps inside.
Bret didn't get his Entry Clearance stamp in his passport until he entered the UK upon our arrival. They asked to see his Work Permit, then stamped both that and his passport with his Entry Clearance.
Bret's company hired an Immigration lawyer to help us with all the paperwork, etc. It really helped a lot! Perhaps your company would be willing to do that? Bret had negotiated that as part of the relocation package.
Maybe someone who is an actual Work Permit holder has better info. I know Bret had to fill out a bunch of paperwork and send it, along a bunch of other stuff like HS and University diplomas, CV, I think his birth certificate and some other stuff I can't recall, to the Immigration lawyer for them to use while applying for his Work Permit. It seemed like quite a lot of stuff. We (Cole & I) couldn't apply for our Entry Clearance until Bret had his Work Permit, but it only took us a few days to get our passports back with the Entry Clearance stamps. Not sure if you have any dependents, so that might not matter to you.
Good luck!
Stephanie