If you are instructing for the issue or revalidation of a class rating, FI/TRI rating, type rating or instrument rating, or examining for same then the instructing hours will count.
Under JAA there is no carry through from multi-pilot IR privileges to single pilot privileges. The only concession is that, if you have previously held a single-pilot IR you only need to complete a revalidation flight test to get it back even if it lapsed years ago, as long as you hold a current multi-pilot IR.
I think that this is the CAA view based on JAR-FCL. The IAA could see things differently.