If you take the option to convert your BT service to broadband only , potentially saving £2-5 a month by not having any telephony at all with BT ( the saving may be more if you have a calls plan that you pay for ) , your ‘old’ number would simply become a spare number , and potentially another provider could enquire with BT about porting the number , using the supposed 30 day window after the ‘cease’ , but it’s a risk , there hasn’t been much ‘chat’ about this new process and if it’s successful or not , ultimately it’s the VoIP company you use that would be responsible for this , not BT , so if it didn’t work that would pretty much be the end of it .
I suppose rather than asking here , you should be asking the company you would like to provide this number if they guarantee arranging this port, after BT dispense with the number .
