Thread “Posh but not expensive London hotel venue – evening meeting” (in Venues & Events talk )

I think I may be asking the impossible in that I would like a central London hotel venue with a meeting room for about 200 for a presentation, but I have a very low budget & don't want any drinks or catering. I only need the room from about 6.30 until 8.30 one to two evenings a month – any suggestions?
Thanks! More