William,
the Blackberry integration is done with a piece of software from a company called Notify. They provide you with connectivity into the BB cloud. Please contact Notify (
http://www.notifylink.com ) for further information.
http://www.notifylink.com/imap4_solutio ... /index.htm
A low bar of entry solution could be to get a six-pack of T-Mobile Blackberry's with a data plan. T-Mobile offers a push mail account that your Scalix server can use, too. So you can have autoforward on your mailbox to the T-Mobile account which will then show up on the device. This is the way I am using it without a problem. Note this of course is not limited to T-Mobile, but I found them to have the best offer at the time. Things may have changed.
Not sure if they cover Guernsey, but I believe so.
Cheers,
sascha.