This is the BROADWAY cast, NOT the UK cast.
The official social network page for Shrek The Musical UK said that there is no news of a UK cast CD as yet (31/12/2011)
They hope to put one out, but they will only do so if there is enough demand for it, so let them know that there is!
I'll say it again, this is NOT the London cast, this is the BROADWAY cast.
If you have yet to buy the Broadway Shrek the Musical soundtrack though, this is the CD for you as it contains the bonus song "I'm a believer".