Veterinary work experienceWatch
Failing that there is one in Watford which is probably the closest LA practice, depending on which side of London you're in, but I struggled to contact anyone there and ultimately couldn't organise anything.
Let me know if either of those will be of any use.
WWOF runs 'Woofers' - volunteers on 'host' Organic Farms, some of which will have livestock. Great for summer holiday work, food & bed usually provided in return for work : https://www.wwoof.org.uk/how_it_works