Im not sure whats going on, sipgate have been very quiet on the issue. As posted above any restrictions put in place preventing new registrations were removed some time ago now and to date users can once again register for a sipgate residential account.
Trouble is how long for? Have sipgate reconsidered or just put off getting rid? Questions only sipgate.co.uk can answer and they are keeping quiet! Nobody else offeres a free UK geographical number in the UK, plenty of VoIP providers such as VoiceHost, VoipFone and Gradwell but they all charge a monthly fee.
If the worst happens you can port your sipgate number to one of those but it will cost you around £20 for the port and a further £2 a month for the number. I would just sit back and forget about it for now, fingers crossed sipgate residential will be around for some time to come.