If you have 500 hours in 2 crew operations you are exempt from the MCC and having to do the full JAR IR 55 hours worth. (minus 5 hours). If you have the 500 hours, you either have to do a check ride on the two pilot type with a CAA examiner observing or if you aren't in current two pilot type flying, a JAR type rating with a check ride.
Quite a significant saving in costs.
From my rough estimate, £13,000 for the IR and ~£2500 for the MCC v's £8,000 - £12,000 for the cheapest type rating.