Well, as I said, depends on if you were denied the medical or if they simply broke off the process.
If you have not been denied it, you do it in another JAA state (eg. Ireland, Czech Republic, Serbia, Germany), then swap it (I believe it is a 20 pound fee). There will be not further investigation from the UK side, as you have fulfilled the JAR requirements in another JAA state.
If you have been denied the UK medical, you will have to fulfill the UK requirements before getting the UK JAA medical.
As I said, you can always do the licence abroad (in Germany / Croatia for example you can use Bristol ground school, Ireland, Malta and the Czech Republic do it all in English too...).