I always wave too, to Mk2s, Mk1s and any funky campers I see, but as before, only if they look like they're into their cars.
Spotted a mint red mk2 northbound on the m5 the other day, so pulled in behind him and convoyed it for a bit. Dude gave me a big thumbs up when I got bored and went past him.
Everyone should be doing the same, it's nice if you've had a crap day at work, are driving home and someone gives you a thumbs up

^^But then again, I suppose that's going against the general attitude of this country at the moment - eveyone's an enemy until proven otherwise....... shame.