If you want the last version of Flash Player for PPC Macs, you need to go here: http://kb2.adobe.com/cps/142/tn_14266.html and scroll down to 'Archived Versions/Older Archives'. The first one on the list, Flash Player 10.1.102.64 is the one you download. More information here: http://kb2.adobe.com/cps/838/cpsid_83808.html
You should first uninstall any previous version of Flash Player, using the uninstaller from here (make sure you use the correct one!):
http://kb2.adobe.com/cps/909/cpsid_90906.html
and also that you follow the instructions closely, such as closing ALL applications first before installing. You must also carry out a permission repair after installing anything from Adobe.
But this may still not help with BBC iPlayer, which seems now to require an Intel Mac (it always did, but PPC Macs worked anyway!). It could also have something to do with Safari. I can no longer watch Flash videos on the BBC website or on iPlayer with Safari, only when I use TenFourFox (the PPC version of Firefox), despite the fact that they both use the same version of Flash Player.