over reving on idle

hi all i have a problem with my coupe SE when it is idling it is running at nearly 2 on the rev counter, when i took it for a service the mechanic noticed that the idle air control valve had been disconected he replaced it and it was then hunting on idle on replacing the connection it was ok for about a month then it started racing at about 2 on rev counter, has anybody got any ideas what to do and where i can get a new or 2nd hand valve from its the one just behind the air manifold nearest to the windscreen.

Hi all just got the over reving finaly sorted it turned out to be the inlet manifold gasket that was torn and the electric bits and bobs in the engine where having to try and compensate resulting in too much air getting in and hence the over revving.