I'm pretty sure if you nose around you'll find quite alot about berus . As Tony Phelps say's in his book 'Poisonous Snakes' , "the adder is fortunate in that it has been the subject of extensive field study".
Where are you in UK ? I'm in Ash near Aldershot Hampshire. Around here we have quite a variety of colour variation including the odd melanistic. But , I'm sorry to say that a few of us have been having discusions on other boards and we have noticed a huge decline in Berus numbers since the 80's :¬(
Anyway , good to meet you . Here's a couple of pics for fun :¬D!! Cheers, Alan