Probably best to let it rest indeed until a future update fixes things....I'm no Linux Guru but I don't mind fiddling around with it, which can sometimes have an adverse effect.  On a positive note : at least the public key issue was fixed .  

I contacted Brostrend on this issue and unlike Tim I had a fast response and finished up with sharing my screen and letting their tech team sort it out. God knows what they did because my screen disappeared but I got an e-mail a few minutes later which said "The problem was a bad /etc/apt/sources.list.d/raspi.list"
The dongle now works. Although I have no idea what their message means it may help someone on here that understands Linux better than me to sort out their problem.

For those who were on the edge of theirs seats wondering if this is fixed in 1.6..... it is.

Tim

Not exactly on the edge of my seat, but thanks anyway. Its good to know that there will be one less challenge when I upgrade to SM1.6
Mike