Spekesoftly - thanks mate. Took your advice and looked up Comtech. Just received their 'Internet Alert Call Manager' model IACM 4000 and plugged it in. Works a treat.
However, everybody be aware that you need to subscribe to BT's Caller Display and Call Waiting (£6.74 per month for the pair). Standard Call Minder (1571) from your own phone is free (£5.99 if you want to access your voicemail from anywhere). Got all this info from an exceptionally helpful young lady at BT sales (0800-800-150)
Any more useful gadgets out there Spekesoftly?
Regards, FJJP