The 25% issue seems to be a general Netflix problem for some - often reported on TiVo and I've had it on my PD3
One of the first things to try is to turn off the box and after 20 seconds restart it; this clears any buffering issues the box may be having.
It really must be isolated to certain users unfortunately. I'm on Infinity 2, about 65-70Mbps, and Netflix gets used A LOT in my house. I've never had one buffer/stutter/ dropout. Playback starts almost instantaneously and always runs flawlessly. So BT are defnitely not pushing a problem product!
Is that directed at the OP or me? I'm connected directly by cable to my HH5!
The box is currently connected via Powerline adaptors. I have tried usung a longer ethernet cable (temporarily because I cannot limbo dance the way I used to do) but get the same results. All other players and the BT entertainment channels on the internet work flawlessly.