Hi, first time here and was wondering if anyone could help me.

I have recently acquired a copy of Douglas Adams' Hitch Hikers Guide To The Galaxy. This copy is, what I beleive to be a little bit special. It is a paperback published by Pan London, and is a True First Edition, what makes it also a little more special, is that it is signed by Douglas Adams, it also has a flyer in the back of the book promoting the book on LP. The book is in very good condition considering its age, and to be honest it looks as it is unread.

I have searched the internet, high and low and cant find another like it, anywhere in the world. I have seen other versions, such as hardback copies etc, but this specific one was released before the hardback ones.

If anyone could help regarding its rarity and a price guide I would be grateful.

p.s. I bought it from a charity shop for a £1.00 and have been offered £100 for it, but im pretty sure its worth more than that.

Thanks in advance