to the best of my knowledge they have

Usual closing times is 3am I believe.

i was upstairs and the corridors are very narrow

Well, as you might expect, Ronnies has had to close whilst this pandemic is with us so you may have to think again for your Birthday treat on May 1st. That said, given that you can get a table closer to the band, the food is really good and, IMHO, I don't think it is overpriced given the venue and the experience. Go for it, when it opens again.

je ne sais pas mais vu l'heure des concerts ce n'est pas adapté à eux, accessoirement ils risquent de s'ennuyer

I don't know but think its likely

It's the late night/after hours club upstairs. We didn't go there.

Apologies for the delayed response. Others have said to check the musicians out of YouTube before booking, which is good advice I'd endorse. Unless you know exactly what type of jazz your fiancee likes (and its a pretty broad church, musically), I'd be inclined to look for a solo female singer (like Dee Dee Bridgewater, Renee Marie among the Americans, or Ruby Turner, Claire Martin or Leanne Carol among the UK options) because they are great entertainers as well as wonderful performers. They also have great backing bands with them. Unless you're late birds or you don't have issues getting home very late, then I'd suggest booking the first house but make sure you're in the queue outside a bit ahead of the door opening time, becuase they allocate the seats on a first come, first serve basis. There are no formal tickets and no reserved seats. Buy Priority seats if you can, the experience is much more intense if you sit in that area of the club. If there's just the two of you and you're at the front of the queue, you might even get a front row table, which is fabulous. Have a great time!!

poor only just seen the question. the dod have a cloakroom as you will know now!