You can port your current house number to sipgate after confirm your address etc, in addition you can use a SIP softphone app on your phone (I use Mizudroid ) to use your house phone on your mobile no need for forwarding.
Finally taken the plunge and upgraded to Sky's FttP - only gone for the "base" tier as its still leaps and bounds beyond what we already have; and it basically halves our bill - go figure.
