Seconded. I like "Heritage Action". It's also reasonably short and is available as a domain name.

How about getting "campaign" into the strapline:

Heritage Action - Campaigning against the destruction of our ancient heritage.

If (and when) the name is decided, we have a further dilemma; do we go for .co.uk and offend the Irish contingent, .com to encompass the world, or .org, which is probably the correct one to use, but is less well known by the public?