For Teeters:
I know of three types of commissions for Met Men.
One, as head of the Mobile Met Unit, said he was RAF Reserve, Wg Cdr, and wore uniform often. This included when he was doing his day job, which was primarily as a civilian.
The Mobile Met Unit were [are?] commissioned in the RAFVR I believe. The early volunteers were given a brief drinking test [port], shown how to salute, and were commissioned. From about 1990 they had to jump through a few hoops including a Vicars and Tarts course. I hope and believe that there are sufficient MMU to obviate any need for the "dormant" category, below.
Lowest of the low were those holding dormant commissions, to be activated by the Sec of State at TTW or thereabouts. These were mostly, if not all, in BFG, and the rank was civil service grade determined except for the boss man.
Thus Flt Lt at Guetersloh as an HSO, then it was Sqn Ldr as an SSO at JHQ as a senior forecaster, then as Gp Capt as a PSO in a "Chief" post at JHQ. A PSO normally attracted Wg Cdr only. All these Dormants had full kit held in stores for them, and their letters of appointment, rather terrifyingly for the proper RAF, gave them powers of command .......... and even a pistol. Regarding messing, I was treated as senior to the Wg Cdrs, junior to the Gp Capts and, inevitably, charged as a Gp Capt.
Fortunately for all of us, the Sec of S never signed the letters.
There is now only one Met Man in BFG [if at all] as adviser to G O C at Bielefeld. I expect he is MMU, sqn ldr.