Touring - Wales expenses

I am considering a tour in Wales for this summer for about 7 or 8 days and I have several questions for anyone who's done a similar ride before.
-How much should I plan to spend on food? From what I've heard food in the UK isn't cheap.
-How bad are most of the roads for cyclists?
-Are affordable and tent-friendly campgrounds (preferably costing less than the equivalent of 15-20 USD) common or should I plan on stealth camping?

I've done a 6-day tour in Wales in 2003.

-- food ... when I was there, the British Pound meant that a $5 burger meal cost 5 Pounds which was the equivalent of $12.5. 2.5 times the Canadian dollar. Things have changed, and right now the British Pound is about 1.5 times the Canadian or Australian dollars. So that $5 burger meal would cost approx. $7.5. Not too bad.

-- roads ... in Wales, at least the part of Wales where I cycled, the roads are small and empty. The thickest traffic jam we encountered was a herd of sheep.

-- camping ... in Wales, when I was there, certain farms were allowed to offer camping. As we cycled along, we could identify those farms by a little sign on their gate. In 2003, we paid the farmer about 5 Pounds (unless he asked for more) for the use of a field for the tent, and sometimes a toilet block. I'm not sure what the going rate would be these days.


My Wales tour ... http://www.machka.net/pbp/post.htm

Update:
I've decided I'll likely modify the "Lon Las Cymru" route to make it closer to 300 miles and follow that fairly closely. How frequent are traditional tent-camping sites along the way?