I’m sorry to hear that and it seems that they are definitely crossing a line. There are a lot of articles on the internet stating exactly what bailiffs can’t do.
On the whole, debt collectors cannot visit your home if you have weak, disabled or people that are sick in the house and in your case they cannot visit if you have young children present.
Unfortunately, debt collectors can visit between 6am and 9pm BUT they cannot be overly aggressive or make your circumstances known to anyone other than you so if the Moorcroft collectors are shouting loudly then this could be grounds for a complaint.
Finally, if they are calling and sending letters so frequently it could be considered harassment then you are entitled to send them a letter stating your contact preferences which they have to stick to and if not you can complain.
The link you asked about is a good start but there is loads of good information available for free online and like I said, if it all becomes too overwhelming, get in touch with a debt charity.
I wish you all the best.