Need help finding title of an 80s UK documentary series or one off

In this short series they followed the life of a family in London (I think) which had a mum and dad and 2 young-ish daughters. The youngest daughter was good looking having long black hair and basically a heartbreaker interested only in boys and partying...her slightly older sister was a bit frumpy looking with short dark hair and was utterly jealous of her sibling as the difference in looks was quite large and the elder daughter always struggled with boys

I think it was called Family Therapy or something. Of course over the series we found out that the girls were basically ok and that a lot of the family issues were down to the father...I also recall they used to let off steam as a family by doing water gun fights

I am fairly certain it was shown on BBC2 on Sunday afternoons mid 1980s . possibly a short series of 4

any ideas people?