As someone with experience on various UK dairy farms, I know quite a lot of farming families that drink raw milk, taken straight from the tank. Saying that, though, farming families seem to have much more robust immune systems- possibly because they're exposed to muck and germs on a daily basis!
On every dairy farm I've ever been to, the cows, goats and sheep have their udders cleaned and dried prior to milking. Some cows do have very dirty udders, so they are sprayed with a hosepipe before being dipped, dried and milked. Their teats are then sprayed with a substance which allegedly encourages the teats to 'seal' and protect themselves from disease. Unlike goats (which do not pee or poo in the parlour, unless ill), sheep and cows have no issue with peeing and pooing in there. That's what the hosepipes are for, to wash down the milking platforms between sides, as well as teat cleaner and wipes.
Milk is taken either every day, or every other day, depending on the milk contract. A small sample of milk is taken and labelled by the tanker, which allows the processing plant to measure the bactoscan (how clean the milk is) and the somatic cell count (if it shows a high cell count all of a sudden, you're likely to have a cow or two with mastitis) and whether or not it contains antibiotics. You receive bactoscan and cell count readings on a daily basis, and you can be penalised if results are too high. You'll be alerted very quickly if you are suspected to have put antibiotics into the tank.
Antibiotics are not routinely given to dairy animals in the UK. They are only administered to treat health problems (e.g. infections such as mastitis), and those cows are then marked both in person and on the computer system. This blocks them from being milked into a normal tank. They are milked on dump buckets, and the milk is thrown away as it is unfit for consumption. Cows that have been treated with antibiotics will be barred from the tank until the withdrawal period has ended. This varies depending on the medication that they've been given. If antibiotics are found in your milk, farmers face large fines and may risk losing their milk contract if it is a regular problem. As milk cheques are a regular payment, nobody wants to lose their contract!
Growth hormones, or ones given to increase milk yield, are illegal in the UK. UK farming regulations are apparently among the strictest in the world, with higher welfare standards. There are penalties if you are in breach of any of these. I have only ever known for hormones to be administered in exceptional cases, to treat follicular cysts, which may cause issues with fertility. Obviously, dairy animals need to have calves to produce milk, so cysts must be treated.
In addition to all of this, milk is sampled on a monthly basis by the National Milk Records. A small sample is taken from every cow, and data is given to individual farms. You can use it to pick out cows which have high cell counts, which might be due to things like mastitis.
TB testing is usually carried out every six months. TB testing days are fraught with tension, because if you're found to have TB on your farm, you cannot sell or move livestock on or off your farm. I've never been on a farm with TB.
There are farms which sell raw milk directly to the public, but they're quite few and far between.