sorry got no advance on maps/books as have found stuff just by riding. Not sure how much of the stuff that is around is dodumented anyway.
as mentioned by you and others muddy moles is good also might find some info here:
http://redlandstrails.wordpress.com/2009/12/
map directions here:
http://www.chocolatefoot.co.uk/journal/wa/archives/2003/02/000060-4_lumps_classic.html
info here:
http://www.diaryofamountainbiker.co.uk/routes_north_downs.php
guided rides with these guys both free and solo at cost:
http://www.nirvanacycles.com/guided-rides.htm
(think they do 2 days but one is quite pacey)
theres also these guys here for friendly advice on trails
http://www.head-for-the-hills.co.uk/
both the last two are local shops and will stock maps… both will give you advice on where to ride as both are involved in building…