less than optimal adder habitat pix.

Looks like optimal reptile habitat to me.

soil type seems to be important, i.e. free draining. a lot of similar grassland sites around here for have no reptiles there will be numerous reasons but i think heavy clay is mainly to blame.

 Lovely habitat Ben and thanks for the pics.

I should do the same!

I tend not to advertise on the net where i've found reptiles for development sites only.

However, I think it is important to give herps the attention they deserve. I have found that if I am talking to someone and they ask me what I work on and I say reptiles,they immediately think of adders, and then say that adders are bad news. 

So i wouldn't want to argue with you at all Ben.

 I would agree that there are more reptiles in unmanaged sites. I've tended to find more reptiles on sites which aren't overly managed by wildlife trusts or a reserve like roadside verges or grasslands which aren't managed as much as a nature reserve grassland might be.

Regarding adders, I've tended to find them in grassland habitat and in areas without bracken. I've also found them in habitats which are covered in bracken (as a young child). However, the soil type is an important factor.

Might temperature be a factor? Clay soils are regarded as cold. Having gardened in the same town on light soil and heavy clay, I know which soil is warmer earlier in the year and produces an earlier crop. Clay holds the moisture better but also the slugs!

Whilst doinIg history research I often come across old diaries and letters that make comments like "Fred Newton killed four adders at...". Knowing the places mentioned I am surprised as many are not what we would consider adder territory today and very likely are not adder territory today. One man told me of an old timer (relative) who regularly used to go out killing adders with a stick and a total of a dozen an outing was not unusual. He was walking along where today you would not find any. The obvious comment is that he killed them all but more likely the habitat has changed.
Knowing these places I have to agree with Brett that in the past a 'much greater diversity of habitats' was used by adders- I am talking about Devon here but I'm sure this applies elsewhere. For my own corner of Devon I can see a much more open landscape in the past. This is a sweeping generalisation but the particular places I read of as having adders are now much overgrown.
The site of the killing of a smooth snake in East Devon in the early 1900s was then a quarrying area with light scrub, now a jungle. Landscapes are always changing and in preserving the countryside you would have to ask at what stage do you want to keep it. In many cases the working landscape of the past was probably more helpful to adders etc. than what we have today (here in East Devon at least). Whilst you might say that conservation grazing on the heaths is going back to practices of the past I really don't know if it's being done in a way it was years ago or if it's beneficial to adders. I've seen plenty of adders and grass snakes this summer but not in grazed areas, so do they cope by moving areas? So going back to Brett, yes substrate is only one factor amongst so many.