What is my XYZ worth? How much is THIS worth? Value my...

Not a great pic, and I don't really know the spec, so I expect to get flamed here, but any idea what this Davy Davies bike might be worth? A colleague is selling it for charity on behalf of the original owner's widow. I've been asked me to find out a bit more about it but only have this pic to go on. Personally I've not heard of Davy Davies, but he's thought to be a British frame builder. Anyone know anything about them?

Thanks in advance for any thoughts.
Not Dave Davey is it? Having read that page, you now know as much as I do!

Sounds like a decent bike, but not a hidden gem and a bit too old to be of general interest; the rear derailleur looks to be a modern replacement: my *guess *is that £150 is the sort of money that should be changing hands.

If it is indeed a Dave Davey, then you may now be able to get a more informed opinion than mine: Retrobike?