You can never tell with a Supersport, I bought mine for £90 from a gun shop down the west country and had it sent to the RFD I use, my local gun shop has one for £150 (not sure what age or condition), I may pop in and have a look, I suppose it all depends on condition and if it's had anything done to it.
I agree with you regarding the Mercury/Challenger style shot cycle, I always thought a Challenger with a Lighting barrel was the best 'pointable' rifle I'd used but when I swapped the Lightning barrel from the Challenger to the Supersport (I know I basically just made a Lightning) it just instantly changed my mind, I'd forgotten how much lighter the Supersport was (I had a Brum Lightning years ago) compared to the Challenger, the thing that really swings it for me is the Supersport Customs stock, that extra high cheekpiece really does make a difference (the same as the Challenger stock is better than the Mercury stock).
I still find it a bit strange when you pay compliments to anything non HW, I know you shoot and own other rifles and you probably blow your mind when you're at a boinger bash shooting what ever you can get your hands on but normally it's blah blah HW this and blah blah HW that
, so it sort of throws me a little when you stray from your HW safe zone.
Pete