Hey Biggs,
Great name. I sold Dublin.net way back in Aug 2008 for $15k (in fact, right here on DNF if I remember correctly).
I had a little bit of content on it - experimented with map layers before Google Maps got big and mainstream. Kinda looked like this
https://web.archive.org/web/20080704182256/http://www.dublin.net/
(Yikes I just found some screenshots in my archives..)
Back then when I sold it, the Geo hype was at its peak and it sold relatively quickly (within a week I think). Interestingly, Brannans subsequently listed Dublin.net in January 19, 2016 for sale at $10k.
Britain.net IMHO would definitely fall in that range. My tip is to market it on Namejet auctions.
Jon