yayyay offer payg voip, call forward, sip trunk and uk domain names
and voip api access
OnRelay have a cloud based mobile pbx that is designed for cellular networks. Its core component is OnRelay’s leading and patented MBX mobility server. MCX also embeds a complete open source software IP PBX (sipXecs). MCX works globally utilising existing GSM / 3G voice and data connectivity.
Sipgate hosted VoIP PBX from ~£5 per extension
ohloh stats suggest that the Elastix interface is mainly written in PHP and Elastix® even sell a VOIP over USB Elastibank™ Channel Bank allow you to connect to any Elastix® Appliance model via USB 2.0 eliminating the need for an intermediating PCI (the solution used by other channel banks).
Elastix® technology partners include aastra, atcom, openvox, redfone, sangoma and yealink !
There are even some Elastix videos on YouTube !