Tosh - Gio gets bad reports, but no personal experience.
I chose Nildram, based upon reviews on
ADSL Guide.
They dealt with BT and co-ordinated my change-over from Home Hi-way ISDN - wonderful not to have to deal with BT!
Nildram's Customer Support is said to be excellent - they told me my first modem (bought separately) wasn't working properly but, with that exception, I've not had to call them.
My only mistake was buying a very cheap modem - I fell for the 'just as good as the main brands' sales patter. Wrong! I changed to US Robotics, was online with e-mails set up in less than half an hour, and no problems since.