Thanks for that input Ian. Everything comes at a price. You may find this a useful link:
A modem from Billion is recommended.
For myself I've decided to try line bonding - also discussed on that site. Hopefully this will double my speed, but at a price. I ordered an extra line from BT in late December. The order was first delayed and then cancelled. A second order was placed and then cancelled - both times automatically by the BT computer. A third order has been placed but no delivery has been promised. Doing business with BT requires a lot of patience and a sense of humour.