How many powerline standards are there? Not that I want to know. Just amazing that BT supplies more than one, and doesn't make it clear. I now have to throw away two powerline adpotors and buy a single powerline adaptor compatible with BT Flex 500.
Is this one compatible? BT Broadband Extender 500 Powerline Kit - Twin Pack
Life is too short for this....
If you forget about using the Comtrend ones, then a single adapter, the same as you already have, would allow you to connect BT Vision to your existing BT 500Mb ones.
If you have to buy a pair, then just use one of the pair, and pair it with your existing network.
You could keep the other as a spare, or if you need Internet in another room.
Its the old Comtrend ones that are outdated, and incompatible.