I was promoted to Sgt with a Med Cat of A4G4Z1 (Perm) in 2003 but had no offer of further service.
The rules changed about 4 years ago - then you had to be within your last 2 years of service before you could be propmoted. Now you are meant to be selected exactly the same as someone who is not downgraded. If you are selected then your file goes to the Med people at PMA who decide if you can be effectivly employed within a post in your trade and rank.