Wheels Up:
I m afraid I do not know the details of the ATPL skill test. You could try LASORS or contact a TRTO training on the type you wish to do the conversion on. The CAA have a list on their website.
Strato Q:
I need to doubvle check the rules havent changed, but it used to be that you had to complete half a full FI course and the test. (I just have an idea this has recently been revised will let you know). The CAA will allow you to convert instrument and class rating instructor priviledges, however you cannot exercise these priviledges until you have been through the usual removal if FI restrictions. ie 100 hours JAA instructing and 25 solo send offs