Well, I have a wee update for you - I went and bought the Panny 50PZ700 today as i was getting frustrated at waiting for somewhere to have the Pioneer LX508 in stock.
I am completely blown away. The HD is superb and SD upscaled from my SKY HD box is amazing. Wasn't expecting this to be so good.
The Pioneer would have cost £3500 and I paid about half that for the Panny. Even IF the Pioneer was better, its not worth double the money. I doubt i would be able to actually SEE any improvement with my eyes.
I have, after months of reading and research on forums, finally settled on the right TV for my main lounge. What a relief I can tell you.