Mark Williams frequents the pub in the village he lives in and is apparently lovely.
He IS lovely, and so are his little girls. DP and I were in a pub garden (possibly the same village pub?) with the dogs, when MW strolled over with his daughters, and asked, very politely, if it would be ok for the kids to make a fuss of the dogs. He was really nice, chatty but not pushy, and he thanked us for letting girls say hello to the odgs.
I didn't know who he was. When we left and got into the car, I said "I'm sure I know that man from somewhere, he seemed awfully familiar", and DP pissed himself laughing, then called me a twat and recited practically Mark Williams' entire IMDB entry. 
I've bumped into him a few times since, and he always says hello, and makes a fuss of the dog if she's with me. One of these days, I may confess that I had no clue who he was, and that I wasn't just being mega-cool.