Fortyodd, Bloo was my boss on 671 and, as excellent a pilot as he is, did not have the answer to this one.
Sycamore - I don't think the starboard lateral lead of the Sea King mixing unit is a factor, the Lynx doesn't have this and still needs loads of left cyclic to roll out from a quickstop/wingover to the right. Upside down in a Sea King - rather you than me, no problem in a Lynx however. As for ETPS - too old and crap at maths!
Nick - just a thought about the slope of the CL curves on the opposite sides of the disc - the retreating side is at high AoA and a one degree pitch change would produce a bigger increase in CL than the decrease on the advancing side which is operating at low AoA (and therefore presumably on a shallower part of the CL slope). The only problem with this thought is that it ought to work the same way in a roll to the left.....ah well, back to the drawing board!