No player is immune to a transfer, I just don't see Villa selling a highly rated 21 year old Scottish international, who's currently in their first team, for a mere £1m. Bannan appeared with McLeish in their press conference ahead of the Blackburn game on Saturday and McLeish was asked about rumours regarding Chelsea preparing a bid for Bannan, he replied “I don’t think Chelsea can afford him!”. Obviously a joke, but perhaps an indication that they're unlikely to entertain a £1m bid?
A player who is playing isn't let go cheaply. In normal circumstances a player who is in the team only gets sold if it is a really good offer and money you can't afford to turn down. These circumstances aren't necessary if your chairman is Paul Duffen for example but usually they are!
Havent Man United got any Midfielders that they dont want that we can have on loan, afterall we have quite a few Man United kids here.