The F lounge is nice and cozy but has a very regional airport feel to it. I've seen it full too many times meaning I had to go to the (also busy) Terraces. BA used to have the lounge over two floors (I'm sure I read somewhere it used to be three - can anyone confirm?) reducing it to one was a big mistake.
The F lounge was much bigger originally and the Terraces (as was/hybrid current lounge) was spread over two floors, connected by a staircase.