No mess kit at IOT? I don't know....standards!
At my UAS I was appointed senior student in 1972. The Boss congratulated me, handed me custody of the badge of office (a quart tankard*) which was mine for the year, then advised me that I would have to get some mess kit....
So off to Moss Bros where a couple of tailors' assistants just like the "Ooh - suits you, sir" pair from Little Britain found me a jacket from the chest of 'cancelled orders' they had, which fitted just fine. About £30, plus Plt Off braid. The only other item I bought was that awful blue cummerbund. I never bothered with proper mess kit trousers and it lasted for the next 30 years, but seemed to have shrunk a bit and was a bit frayed in places - like me - by the time I retired!
Incidentally, that wonderful source of pre-owned RAF uniform, Ernie Bedford of Newark, is no longer with us and his shop has closed. He was struggling to get sufficient stock in the late '90s as I discovered when I tried to source a blue waistcoat..."I'm very sorry, sir, but the Service is so small now that they're very hard to come by". Such a nice, courteous gentleman in the true meaning of the word. Fortunately I managed to get one from a mate who was off to the airlines!
*I was glad to see that the ULAS Senior Student's tankard was still in use some 40 years later, so claimed it as mine for the evening!