if i was you first of all i'd chill out - no large charity is going to "steal" your idea and use it to get money for themselves (though if it is truly inovative i wouldnt disclose what it is on a public forum)
secondly you say "green issues cant wait for 6-12 months" if its a campaign issue i'd be inclined to forget access to nature because the fund isnt for that. I'm not sure where you got the six to 12 months figure from but you can submit a grant application as soon as the funding bid opens which is described as early 2008
thrdly the funding is being provided by natural england and lottery and NE are managing it on behalf of a consortium of organisations drawing on their skills to assess bids - these organisations are not competing for funding.
fourthly you wont get any money until you tell NE what your ideas are so they can assess their viability and applicability
fifthly you need to provide match funding, though for small ammounts (under a 100k) this can be provided in your time rather than in cash - if you do need cash for match funding look at landfil tax providers such as biffa, shanks first, sita trust etc.
and sixthly as far as i know wab isnt applying , though even if we were it wouldnt make any difference to our willingness to give advice to people such as yourself.
If you would like me to look your idea over and give more specific advice feel free to pm me more detail - i promise not to nick your idea ( I work for a hosted project funded by NE and thus inelligble for this funding anyway)
good luck
btw if anyone else is interested this is the link to the access to nature pages
Access to Nature - Natural England