I believe (but do not quote me!) that once you have reached a certain threshold you can go down the 'self study with no brush up' route with the consent of the UK CAA and your study materials supplier. This could apply only to ATPL conversions - like I said, don't quote me!
Get in touch with the UK CAA. If this is the case, make sure you have any dispensations in writing from the CAA.
Update: Section D1.5 of LAS 2008 covers non JAR CPL(A) conversion requirements; E1.2 (page 4) of LAS 2008 covers conversion of ICAO IR to JAR IR.
Last edited by rmcb; 9th December 2010 at 13:40.