UK Incoming geographic number, reachable locally or from anywhere, can be obtained for "free" with a purchase of 10 British Pounds of calling credit from
DrayTEL VoIP Service, with no ongoing charges.
This is not a true DID, but a VOIP account with an Incoming UK number. The account can be registered in Voxalot, and the audio quality is very good.
Voicestick is also offering free UK numbers, but these cannot be registered in Voxalot so far.