For CofA or permit renewal air tests in the UK you need to be specifically approved by the CAA. For light aircraft this will require as a minimum 500 hours for singles or 1000 hours for twins and a briefing (in person) from the CAA flight department.
For big aeroplanes you must actually do a check flight with the CAA test pilot to get approval.
Download
http://www.caa.co.uk/docs/397/srg_fl...1-05102004.pdf