It depends on the domain.
If it's a good one (ie. keyword rich, no hyphens etc.,) then you might find Sedo would work well. Selling via one of the many domain forums can work, but the price you get will vary a lot.
Whois privacy is quite common and registrars aren't under any obligation to reveal registrant details unless a law has actually been broken.
It's unlikely that you'll be able to do much directly about a site that is providing critique, so you'd probably be better off focussing your energies on getting the "real" site's rank up on the search engines
It's not a big deal for the registrar to make that change for you.
The only time it gets messy with a co.uk is when you have to change the actual registrant part ie. if the domain was registered to you as an individual and you want it registered to your company instead
We've got it enabled on several of our shared windows servers and will be making it available on more of them soon.
The funny thing is that very few people actually ask for it