@SYNACK: I looked at that and couldn't seem to get enough info about whether it would do exactly what I wanted.
I've ordered the Positron device - It appears to be fully-fledged Asterisk and has more ports and the echo cancellation. It was only an extra £50 too.
@kylewilliamson: From everything I could find about the Linksys device, it didn't contain a SIP server. The FXO port connects you to the PSTN, the FXS port connects to your analogue handset and the ethernet port routes out to the Internet to connect to a VoIP provider. Basically, it means that you can use your current analogue handset and automatically route via the cheapest call route.
It's late but IMHO that doesn't say a SIP phone can route out the analogue line. It doesn't matter anyway because I pluped for the Positron. I'll let you know how I get on - it might also serve a purpose on our non-IP Avaya IP Office at work ;)
Originally Posted by kylewilliamson