That's largely irrelevant Jay. If your worry is keeping the same number so people don't have to learn a new number, you'll no longer be covering the same area so everybody will have to learn a new number for you anyway as a new business in the area.
If your concern is changing your business stationery, you'll have to change address on your letterheads anyway. Only really your business cards that you'd have to bin.
I did a fair amount of research into this when I started out - surveys etc. What I learned was not to underestimate the power of "local". A surprising number of people distrust firms with only a mobile no. They feel that 0800 numbers mean the company is big and faceless. Hotmail/gmail address makes people doubt the firm's solidity and authenticity - anyone can set one up.
People do trust landline numbers with local area codes because until fairly recently you had to show ID, proof of address etc. to get a landline. Most people aren't really up to speed with how easily available virtual landlines and VOIP are. A mate of mine has got something like 12 separate landlines, to cover all the local dialling codes, eg:
020 8521 1234
020 8524 1234
020 8527 1234
The number of people who say "Oh, your just round the corner!" is huge, and it makes him seem more trustworthy. It really is a big thing for people to think that you're very local. It's comforting. These lines all tap into one main line, diverted to his mobile or any other number, and cost about £2 each.
If I were you I'd spend my money on that rather than 0800. Bear in mind also that many younger people nowadays don't have landlines, only mobiles, and not all providers give free calls to 0800 from mobiles, but everyone gives free landline minutes. Add a mobile number for texts and you're golden...