there is a bt trials team and a website where you can register as a volunteer, each specific trial is invite only but that will be the first step towards getting picked.
I think this is the url
I was only on there for a year or so during my time on infinity and I got invited to 5 different trials, of which 3 I took part. They even kept inviting me for stuff for a while after I left BT
Getting free stuff is nice, but after taking part in trials I realised the real value is having a real say in the products themselves, its the only part of BT that seems to actually listen and take in feedback from you. If they reject your feedback they then explain why as well which is nice.
Edited by Chrysalis (Mon 21-Aug-17 00:30:30)