I use the Vonage service for both home AND business, with it diverted to another number if the Internet dies.
Vonage offer a lot of extra services, which is where the virtual numbers come in, basically when you sign up it asks you where you want your number to be, so if you wanted a local number you'd pick 0151, but there's nothing to stop you getting a number from anywhere in the country, just remember that if you make local calls you'd still need to dial 0151 as you would, in effect, be dialling from a (for example) 0161 number.
The basic package with Vonage will cost you £5.99 a month, they give you a little box that you plug into your router and you plug your phone, or wireless base for cordless handsets into that, and basically that's it.
Caller display is free
Call diversion to another landline is free
Withheld number rejection is free (gets rid of a LOT of telephone sales)
Standard landline calls are included in your £5.99 but you will be charged for 0870 and 0845 numbers, but if you type them into www.saynoto0870.co.uk
you can usually find a standard number.
Mobile calls are 15ppm daytime, 10ppm evening and 5ppm weekend (currently)
I've been with them for about 8 years, call quality was a bit hit and miss in the beginning, and I soon learnt that no one could hear me if I had four computers hammering the torrent sites when I tried to make a call, but that's got a lot better over the years (although granted I do now have 100MB line).
I've recommended them to a few people, and if you input my username when you join (TheDr-UK), we both get three months free rental, so if you get four people signing a YEAR it costs you nothing
If there's anything else about it you want to know just pm, I've been with them so long I even have equipment they don't offer anymore (phone that looks like a mobile with a landline number that works off any wireless network, very useful).