Put simply, you have a non ICAO licence therefore it is not automatically accepted by other ICAO States. However, if you write to the Aviation Authority of the State you wish to visit, then it is up to them whether they allow you to fly there or not. As most European States do not have such a robust system of Microlight licensing as the UK, they are happy to accept the UK Microlight rating as being at least equivalent to their own system.
The more complex area is the SLMG; the old UK PPL SLMG (40 hour) was an ICAO licence but the current NPPL (35 hour) version is not!