Very good idea Stu. I have currently similar set-up on my Fritz ADSL modem/router. Just to let you all know, one of cheapest rates to call IOM mobile as well as UK mobile is using
http://www.webcalldirect.com/ , which one of Betamax( formerly Finarea) site. SKYPE is still ahead, but I don't count it as a regular rate. The rate is 8 Eurocents plus VAT.