Seddons were not something that featured in my own professional landscape in days gone by. I once went to see if there were any jobs going at a small Nottingham firm (Hutchinson’s or Huskisson’s?) who ran Seddons but never drove one until I became a self-employed car dealer after leaving Stirland’s.
To supplenent my lack of Arthur Daley expertise I worked fairly frequently for Stirland’s on a casual basis and they once had me fetching some trailers in from East Anglia with a trade plated, primer painted, Motor Panels tractor that they apparently kept for the purpose.
The drive was ok but nothing out of the ordinary to dispel my ignorant belief that they were the poor relations of British lorry makers. I remember being amazed that it was them, rather than the rumoured Fodens, that successfully absorbed Atkinson. That was after quelling my amazement that my beloved Atkis should need absorbing. 
This thread has dispelled a lot of that view and I now see them in a new light. A manufacturer of a premium truck at a less than premium price. (I am especially impressed by the power steering on the 8 leggers, essential in my view in reversing a drawbar the ‘proper way’ rather than nosing it blind. 