Not exactly right on the doorstep, but The Beeches is just over the bridge and has wonderful views and a pretty good pub (called the Anchor IIRC) a half hour walk through the forest away in Tintern.
http://beechesfarmcampsite.co.uk/
Word of warning though, watch out for the fire pits (which are a great touch) when you're driving around. They are made of old truck wheels so pretty hefty. When we were there at the end of July this woman set off in her CRV with trailer tent behind her, not looking where she was going, and drove straight into one. It kind of rolled backwards, and lifted the front wheels a foot off the ground! Lucky she had 4 wheel drive or she'd still be up on it now. Went and had a little look underneath for her as she wasn't sure about driving off, expecting split rad or oil cooler hoses, maybe drive shaft or sump damage- but she'd hit it bang on the jacking point on the lower cross member. Not so much as a scratched under-tray!
We're planning on checking out Petruth the 1st weekend in September, will feed back then but it does look good.