You are a rare bird. That may not come as news to you -- but if it's of any use, here is the best article I could find easily:

http://en.wikipedia.org/wiki/Haplogroup_N1a_%28mtDNA%29

Mostly I follow forums based in the USA or the UK, where people post in English -- but your haplogroup is uncommon, either place, so they rarely if ever mention it. Here's one thread from a more continental European forum that's conducted in English:

http://www.eupedia.com/forum/threads/25930-mtDNA-N1a-how-rare-are-we

None of that tells you anything about why your genetically rare ancestresses were in the Forest of Dean, though.