ISDN or ADSL Broadband for real time remote recording?

As a UK Based Studio Manager for a voice-over recording studio I'm looking at opening up our voice portfolio to include real time remote recording globally.



The problem is deciding which avenue to go down: ISDN or ADSL?



ISDN is an established method with many voice-overs but I fear this is going into decline. BT recently announced they were axing ISDN for domestic users. They will have to switch to a faster ADSL Broadband.

http://www.itpro.co.uk/networking/news/109397/bt-to-axe-isdn-for-domestic-users.html



A professional ISDN codec for the recording studio may cost around £2,500 which is a large investment.



Recording through an ADSL Broadband Internet connection may be a better alternative.



Does anyone have any experience of conducting real-time recording sessions over the internet? Are there any issues?



Are there any problems guaranteeing enough bandwidth for the session if there are multiple users of the connection?



What specialist hardware, software & connections are required?



Any help on the subject would be greatly appreciated as I can't find much specialist info on the web.



Thanks :?