Well, as these things normally go, it was a frustratingly simple fix for iplayer which after months of messing around I delved back into after posting here. Turns out my DNS settings were not quite right for my router so after I had sorted that out I used the SVN Repo Installer (which in turn, due to the incorrect settings hadn't worked properly either) to update it.

I had unknowingly been using a waaaaaaaaaaaay out of date plugin so after that was installed along with the correct DNS settings it woks flawlessly! Its a nice little way of catching up in comfort rather than being sat in front of the lappy t!

After having a look on the xbmc4xbox forum the youtube pluggin seems to be having issues for everybody atm unfortunately. Now mainstream support has been dropped for the xbox version things like that might take a while to get sorted, if ever.