I'll bet there will be the odd one or two lurking unloved in some houses, neglected and gathering dust.
Yes, I'm pretty sure the Whaley Crosman was based on the 761. I can remember Rod Linton testing it for Airgun World. If I remember rightly, you could put a load of pumps in and get two shots. Or you could put a load of pumps in and just keep topping it up with a few, but if you lost track of where you'd got to consistency would suffer. Whaley obviously did a lot of work on the pump assembly, valve and hammer.
I'd guess that it never gained mega popularity over here due to a number of factors :- our home produced guns were springers, and pump-ups will have seemed like far too much work for not that much return, although recoilless. The Crosmans always appeared to be built quite flimsily, creating fear of poor reliability/longevity. If you were a Crosman fan, most would go for the 766 (still available now as the 2100), due to,it's higher power. These all paled, however, when compared to the earlier, more solid Crosmans.
And, if you were a fan of American pump-ups, all these more modern Crosmans lived under the shadow of the legendary Sheridan Blue and Silver Streaks, with their solid build and promise of magnum power levels.