UPDATE - BBC iPlayer stopping halfway through a program
RE: this thread..
Finally, after speaking to two Philips and three John Lewis ( retail store) tech support operatives, a fourth tech support rep from John Lewis finally had enough knowledge to explain why BBC iPlayer was not working properly on my tv.
It must be noted that my wifi signal is very strong and that my Humax PVR and PC's do not suffer with any problems running iPlayer. I checked my Wifi signal with http://www.broadbandspeedchecker.co.uk/ and this returned a download speed of 28.48 mbps on a linux pc positioned further away from my wifi router than the tv (42pfl7666t).
The tech support from john lewis store recognised the problem I had as he had other Philips customers reporting the same type issues, although he didn't mention if they occured while using iPlayer.
The solution was to change the router encryption from WPA to WEP. The explanation given to me is that WPA uses an extra amount of wifi bandwidth and this loss of bandwidth causes problems for a wifi enabled tv as the "wifi Card" (their desciption, not mine) built into the tv is not as good as those built into my pc or pvr. I'm not sure about that, as I think it's more to do with the tv not being able to buffer enough data while streaming, especially on hd tv programmes. But only Philips can explain exactly why the type of encryption should have this affect
Hope this helps anybody with similar problems, I'm disappointed in Philips being unable to suggest this solution.