Yes they will get a UK CPL but as I understand a national licence will only allow you to instruct in annex 11 aircraft.
I had a hybrid JAA CPL issued on the strength of UK CAA (14 yes 14 CPL exams ). I retook my exams for advancement of my aviation career but due to the recession I am unable to complete my IR, (just cant justify the expense) and with the IMC remaining dont really need one, but I used the exams to upgrade the hybrid CPL to a full JAR CPL so some use to taking more exams. I also have got more into ground school so that also helped.
I was told that my licence would have only been valid on annex 2 aircraft because without the JAR upgrade it would have reverted back to UK CPL.
If you really want to laugh I have been told if EASA dont allow the IMC to be added to the EASA CPL as an IR(R), the CAA will reissue me a UK CPL to place the IMC on, so back to where I started pretty much.
What a bloody mess this all has become.
Do you remember on PPRUNE instructors section all the questions used to be about instructional technique, students and flying in general, now it is all about legislation, sad really.