PR automatically drops down to "google does not rank current page" whent he "whois" changes.
i.e. the PageRank of that site does NOT get transfered over to the new owner.
Aged domians are good, but really need to be close to (or over) 10 years old atleast to get any true benefit.
But once a domian name has no website on it and google caches that page (like clean-carpet.co.uk) then again, pointless in terms of SEO benefit.
Soooo, the only true benefit here is the backlinks.
Text links ads.com, nothing new and a very costly way off gaining backlinks!

Derek, the cost of those domians are what ever your register will charge you. Namecheap for example will cost $8.88 for 2 years. all .co.uk domian names are for two year at a time.