Actually FF, they aren't. I've got a JAR license with a microlight rating added too, but...
It seems that those super blokes in CAA personel licensing decided a month or two ago to decide without consultation with anybody to stop doing this and insist on new NPPLs being issued, along with the required fees. This is mind you the same people who used to decide that 1000+ hr microlight pilots could only have 10 hours off the requirements for a PPL(A), which made just about as much sense, and was done with as much consultation.
Their latest I understand is that they're also trying to stop PPL holders obtain microlight instructors ratings, which since there isn't a CPL(Microlights) would apparently prevent almost anybody ever becoming a microlight instructor.
A little bird tells me that all this was decided unilaterally, recently, and without even telling the BMAA who are understandably hopping mad about it.
G