After many months of this working, today I hvae disconnected everything to tidy cables up and dust/hoover behind my TV unit. I am now back to square 1 with the BT box being unable to connect to the internet. No matter what I connect or boot in what order, it is not working through the GS205 switch. It appears whatever I did was a fluke.
This is really really frustrating and it shouldn't be this hard. I'm considering leaving BT as I'm sick as a chip ;-(