This sounds daft but want confirmation…
Basically our BT Infinity has been crap lately. Buffering when watching iplayer on the TV, no hope in hell of watching it on Hd etc. I’ve also noticed that music getting streamed off the Pc to the hifi downstairs is partially knackered. It’ll play maybe half a song and then stop and pick up where it left off so I’m thinking it sounds like it’s buffering the music but it’s not coming off the net, it’s off the pc within the same home network. Would crap service from BT cause this? Might be nicest have extra ammo when I call them tomorrow (and if it is that,it mmeans I don’t need to go fault finding!).

WiFi or ethernet connection to router?

I don’t see how your broadband could have anything to do with your LAN problem. Your router could easily be responsible for BB and LAN issues though.

Wifi. Yeh, did think about the router. ****. Time for problem solving 🙁

I would suggest using inSSider to take a look at what other networks are around and give yourself some channel seperation. If possible move on to 5 Ghz wifi or cable it up for best performance.