Draytel.org a VoIP provider offer a Pay As You Go (PAYG) basis you get an 870 number and you can top up at £10 a time. Uk land line rate is 1.4 pence per minute and Mobile phone rate 11.9 pence per minute.
Mobile phone service improvement
Are you struggling to get a mobile signal at your home. On some networks you can fix this problem with something called femtocell.
Vodafone Sure Signal,
EE Signal Box,
Three Home Signal device.
All of these solutions use your fibre broadband connection to reach their network. The box will then output a local GSM signal for up to 3-4 phones to send or receive calls, texts or data at once, in and around the house. Cost vary from free to £50+