You've found some interesting bikes
The Mercian looks the best of the bunch but I'd take that frame number 0129 and drop Mercian an email, I'd want to confirm that is a Mercian. They are always really helpful.
The Carlton doesn't have a great paint job and the lug lining is pretty poor.
The Raleigh is a tank but interesting, although a 3 speed Sturmey Archer gear is a completely different ride to a derailleur.
The Hetchins isn't cheap unless they will do something for cash? But then you have the sourcing parts and total cost problem.
Unfortunately, this may be to big but its nice and original:
http://www.ebay.co.uk/itm/Raleigh-Carlt ... 1e7a943d5e
This could be a hidden gem:
http://cgi.ebay.co.uk/ws/eBayISAPI.dll? ... ink:top:en
Campag, drillium, nice lugs
Its never straight forward