TVM, mad_jock. Your first link lead to another, which lead to another, which has ended up with me ordering a Plantronics C65 DECT GAP headset from Amazon.
It just occurred to me that my BT Home Hub v1 is DECT GAP compatible (the non-BT DECT phone in my garage is connected to it so I know phones other than BT Hub phones do likely work). If I therefore synch the C65 headset with the DECT facility in the Home Hub I can not only hand calls over to other handsets in the house with ease as they will be on a different base station but I can use it for my I.P. telephony too.
Cheers,
XV