[eeyore]

My advice is to try early morning just after the sun comes up, you might well find adders, (and grass snakes) sunbathing on flat rocks in order to warm up their blood. also what about contacting your local reptile group (see the froglife website for details). Holton Heath is good but its restricted access because of the number of holes, trenches, and chunks of abspestos lying arround ( it was a munitions factury during big mistake number 2).

Also don't get bitten, I've been bitten by adders twice - both times while brush cutting heathland habitats, nasty my leg swelled up like a zeppelin and I had to call 999 from my mobile because there was no way I could drive.