I know it's most likely a 1981 model as Barry Waddell's name is shown as the seller and the original purchase date date is 1981 on the accompanying owner's manual
Another way to check its age apparently is to examine the rear hub, if it has Sturmey Archer hub gears you should find a date stamp somewhere on the hub shell. If it reads 81 followed by another numeral then it was made that year and the month.
I've only known one Bickerton owner back in the seventies who was considered quite eccentric using it as intended. That is riding to the station then folding the bike and placing it in a bag (carried draped from the bars when riding). Then carried onto the train and unfolded to ride it to and from work. I have no idea of their worth.