I will explain, however that will probably kill the humour - there is lots of understated stuff.
The 1975 Sex Discrimination Act was a law that made it a criminal offence to pay a woman less for the same work as a man, and also that it was an offence to restrict access to employment on the basis of gender - but in this case there are certain jobs that a female just would not be…er equipped for - hence the stud bull and a field full of lovelorn cows
The British summer weather has always been stock in trade humour, whenever some event is planned it is usually awful weather - here the Giles family has gone out to an agricultural fair, the adults are not at all happy but there is a stoic duty to pretend it is fun for the benefit of the children, one of whom here has just won a pig and is very pleased with it - but what are an urban family going to do with a pig? Its the last thing the father wants on a rotten day. Dad is being scolded for not pretending to be happy for his son’s good fortune
This is the soccer hooligan, and he is trying to prepare a defence for his loutish actions by putting the blame on some terrible tragedy in his childhood - I suppose its really a condemnation of the ‘understand the criminal, and understand the crime’ when there is actually no excuse whatever for being just a yob - clearly this one does not intend to take responsibility for his actions. This is critical of all sorts of things, of our society going too soft, of our criminal justice system which is sometimes seen to be too forgiving on the basis of spurious extenuating circumstances
Ah, wonderful children and the games they play. Here the kids are slamming the door as hard as they can in an unfeasible attempt to make the house fall down, the joke, as any parent of a large family knows, is how the mom is completely unperturbed by this disruptive behaviour - as a parent knows, you have to find ways of tolerating such actions merely to survive the experience of children entertaining themselves in the loudest way possible.
Clearly the other adults, who are tea drinking guests have not developed this immunity to extremely noisy children.
It seems here that dad did something stupid, possibly to impress his son, maybe its just a man thing, but he has entered some sort of competition and won a bright shiny new speedboat, and the son is like - wooaa this is way cool, full of boyish enthusiasm.Of course the boat will need lots of work and money to keep it all together and ultimately its just a big boys toy
To get this joke you have to look in the kitchen window, at the domestically overworked mom who has overheard the conversation outside - you just know there is going to be a huge row.