Xusia,
I was intrigued by your question and I asked about this movie on the mailing list for members of the Magic Circle (P&J is regarded as a sort of kindred art.) As I expected, someone there came up with a possible answer. This is from his reply...
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"Bert,
"I think I have found it...
"KILLER PUNCH (1982) - one of the three shorts later compiled into the feature SCREAMTIME; this one's about a Punch-and-Judy man who brings the traditional seaside story to life, with himself in the role of the psychotic Mr.Punch.
"The information appears on the website:
http://www.british-horror.fsnet.co.uk/HTML/short.htm
"I then looked up Screamtime at imdb.com, and found that it was made in 1983, which fits in about the time you were expecting. For further information take a look at:
http://us.imdb.com/Title?0086263
"Hope this helps.
"All the best
"Gordon Drayson"
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Bert
http://www.bertcoules.co.uk