Animal health visit everyone around us (Yorkshire) when they get cattle. Not sure why cattle are deemed to warrant a visit more than any other livestock to be honest.
Our last visit meant going through some paperwork (standard questions 'what animals do you keep' 'how many of each' 'who's your vet' etc). They then want to have a look at your medicine books, and any movement books for other animals. This is a good opportunity to ask any paperwork questions you might have. They'll ask what you're planning on doing with the cattle- dairy, beef etc. They'll want to see where the animals are kept, if there's enough grazing & shelter for them. They'll also take samples of any feeds you have to make sure you're adhering to regs. They'll ask if you have a cattle crush etc, then inform you to contact your vet in a few weeks to book a TB test etc.
I'm sure there's a few more bits and bobs Ive missed out, but largely its to check that you have everything in order to provide for your livestock properly and according to regs. We've had a few visits and they've usually been and gone in about an hour.
Top tip - make sure your medicine book is filled in correctly and up to date
HTH