I can remember watching Diff'rent Strokes when I was very young (around 4 or 5) in 1984-1985 and I remember seeing the series again on Sky One in the early 1990s. I have found out in more recent years that the series ran until 1986 and that later on Mr Drummond remarried and his new wife Maggie had a young son, who was basically the "new kid" in the series.
Did ITV show the later series of Diff'rent Strokes? I can't remember seeing Diff'rent Strokes in the Central region in 1987-88 which I guess is when the last series would have been shown in the UK. I personally can't remember seeing the series after 1985. Apparently, when Maggie and especially her son Sam were in the series, it wasn't as popular and websites have said that it had "new kid syndrome".