I sold my trad plus 8 in 2012. Prior to selling I was advised that it was worth £33k however when trying to sell I had plenty of offers in the £25k region but did eventupally get £28k when the right buyer came along.
At the time I put it down to the lack of free cash and the more stringent requirements when trying borrow money.
However I have notice good cars still aren't selling in the plus £30k range and its also my belief that the market has changed. After all why should a tidy plus 8 be be worth the same as an tidy early Aero 8.