Veterinary medicine work experience help??

You're off to a good start already. For further ideas, anything with animals is acceptable but to have a good mix of experience I would suggest going to at least one placement each in a small animal clinic, equine husbandry, a commercial farm (so you've done all those if you get your lambing), plus a large animal clinic and a kennel/cattery.

I live in London as well and really struggled to get large animal vet work. There is some if you go out a bit into the fringes but what I ended up doing is travelling away and staying in the cheapest B&B I could find. Worth it in my opinion. Kennels and catteries are much more easily found here, although a lot turned me away when I tried. You just have to be persistent (call if they don't answer emails, keep trying different places) and be prepared to travel within the city.

After you've done the basics, more potential placements could include labs (like you said), zoos, rescue centres, pet shops, dog grooming parlours, urban farms, abattoirs, farriers, aquariums, hydrotherapy centres, falconry centres... like I say, anything with animals counts as long as you can relate it to vet med. Be aware as well that some universities' work experience forms only count a certain amount of 'other' work experience, and are keen to see more vet and farm work. I live in London as well and I was able to get to more than half of the places on that list; London may suck for getting farm work but it makes up for it in other ways

Best of luck with getting some more placements