Check out CAP 804
Part Q subpart 1 has Validation
Part Q Subpart 2 is Conversion.
Keep in mind regarding the conversion route holding an ICAO ATPL, doesn't necessarily mean you meet the experience requirements of an EASA ATPL.
Same applies for the validation path, except the experience requirements are considerably higher than via the conversion route, and your required to convert it anyway (normally 1 year)
Last edited by vh-foobar; 17th Apr 2016 at 14:07.