ArgyleMoss,
I think we have a definition difference here.
With your BT adapter you can use your standard analogue or DECT phone without modification to make and receive calls over the Internet. There are many services such as this with or without an adapter. When you use services such as www.call18866.com you call goes over the Internet, but the last mile to your house from the exchange is still standard analogue.
However end-to-end VOIP requires the handset itself be an IP protocol device.
bwaje asked if the Beocom 2400 is VOIP compatible and the answer is ALL analogue phones are compatible if you have an adapter. However, bwaje appears to be looking for a solution which does not require a device which has to be connected to the mains power in the same way as plugging the Beocom 2400 into an analogue phone line. Unfortunately, you will always need power for the adapter
So, bwaje, any solution including SkyPE will need a power supply.