I used to get stuck behind one in the traffic to work on a regular basis - and this was well within the last 10 years !!! Pretty sure I saw one on the road not too long ago too.
You could get deliveries of regular milk, half top, double top, cream, yoghurt and eggs I think from most of these guys. In latter days most were operated by 'Unigate'.
Check out the Father Ted 'Milk Float' episode - a classic.