As someone who is in a similar situation, I am using a virtual office service from http://www.answer.co.uk/. This is a PAYG service whereby they can give you a local number or you can buy your own number. Whichever number you use on web-site, business cards, etc, It will get re-directed to http://www.answer.co.uk/ and they take a message on behalf of you or will divert a call to your or anyone's mobile depending on the setup.
I have found them to be extremely professional and very helpful and so far this this PAYG service works great for me. They provided me with a 0207 number anyone calling this number can leave a message for me which is then emailed and texted to my mobile and then I can act accordingly.
They also have a JAM service and PURE JAM service. Have a look here http://www.callcentregenius.com/