Long story short I got my parents an Airport Express when their Tivoli CD player died. I thought it would connect to their wifi and the Tivoli, then they can broadcast music from an iPad.
However in a furious attempt to connect it last night all I can manage is very short blips of sound from a Windows PC from iTunes, however it shows up as a second wifi network, so one must switch the device to that network in order to use Airplay, however this means that the device (whether PC or iPad) can't use the net obviously.
Part of the problem was I didn't have their iPad to use for the initial set up and was using my work iPhone instead and (after a few beers) struggled to find the ability to set it up joining the network rather than creating it's own wifi network.
Sadly I'm not at their place for another month or two, but I'm certain that the way I've got it at the moment is not the correct method.
The Airport is plugged into the stereo, not near their router though it could be moved if it need initial configuration.
(Don't get me started on the process of getting their CD's onto the iPad via completely full laptop, sigh)