Hmm, just to reply to my own question. After two months they charged me £15 on top of the £10 deposit making a £25 charge for porting my number. So I guess thats the new sipgate starter price. They said they had had payment issues that meant it took a while to charge me.

Rather scary that having signed up to basic and yet recieved starter they have now discontinued both plans. Hope I haven't paid £25 for a service I can't afford... Fingers crossed they will honour old plans or have something else up their sleeve.