Hi Trishb:
I assume you are wanting to vaccinate for Marek's? I have ordered different vaccines from a company here in the USA. They pack them with ice, and ship them 2nd day air I believe. I'm not familiar with vaccines in the UK, but I assume you should be able to purchase from a company there. The vaccines are not very expensive, but the shipping can be.
If you are vaccinating for Marek's you would do it when they are less than a day old. It involves giving them a shot.
If you are vaccinating for Newcastles/Bronchitis you can just mix it with the water (which is what I did).
My fowl pox vaccine had a little needle that had two points that you stick in the web of their wing (when they are 6+ weeks old for the vaccine I used).
Most folks just vaccinate their chicks for Marek's. I'd check in your area to see what the predominate chicken diseases are.
For Coccidisiosis, just start them on a medicated chick starter till they are about 8 weeks old...