If you're looking for pay £x.xx per month and get 'unlimited' calls - Voipfone is not the answer.
If you're looking for a VoIP service with lots of functionally - suited to small businesses then Voipfone could be the answer.
Sensible priced call charges, ring groups, voicemail, call transfer, music on hold etc. most of the features are listed on the features page.
There is no monthly ‘Line Rental’ with Voipfone – you pay for the services you require. The prices are on the prices page.
Vonage supply you with hardware I think, which is locked to them. Voipfone don’t supply ‘free’ hardware like Vonage, but you can use any SIP compatible hardware. There’s good number of open SIP networks out there, so once you have some decent hardware you should be able to use it with most VoIP providers. Snom phones are brilliant for serious business use.