No, we don't charge a penny. Registration is free and there are no hidden fees. For calls to be free, just make sure you have calls to UK landlines (01,02,03 numbers) included in your mobile/landline plan. This means that the call to our 033 3232 3000 number will be included in your bundle.
OFCOM has confirmed the calls to 03 numbers must be treated the same way at 01 and 02 numbers and form part of your free minutes bundle. You can confirm this at http://ask.ofcom.org.uk/help/telephone/03number. But do check whether your provider caps the duration of free/bundled calls (eg. to 90 minutes) - if so, just hang up and dial back to keep the call free.
If for whatever reason you don't have free minutes, then the call to our dial-in number will be charged as a standard UK landline call - so it will still be cheaper than most competing conference call services that offer access through expensive 0844 and 0845 numbers.