Air France has a lounge at MAN T2 and you should be able to use that ... I have no idea about the Servisair lounge, wouldn't expect Skyteam to be using that at all. The AF lounge is small so it may be capacity controlled, also it is pretty spartan, not lavish like the BA lounge at MAN. T2 is pretty poor as a terminal with not much to do there (it is spacious but bare). I try to make sure I fly out of T3 at MAN, much nicer there.