Yeah, work experience in an abattoir is definitely a good thing - they love it! Yes, there will be blood and everything but you'll get used to it after a while.
I spent a day in an abattoir before I applied to vet school and I learnt loads about food hygiene and stuff. I was just observing but I don't think you can do anything else apart from watching anyway... I got asked about the experience in 3 out of my 4 interviews and basically I told them what I saw and how that was related to the welfare of farm animals, food safety and public health, and stuff like that.
I did have difficulty looking for a place that would take me in the first place (some places won't take you if you are not a vet student yet) but in the end I did find one. Here are the details:
Sturminster Newton Abattoir (licence no: P2140)
Manston Road, Sturminster Newton, Dorset, DT10 1BQ.
Tel: 01258 472227 Fax: 01258 473581
They do bits of everything: beef, lamb and pork so you'll surely have loads to watch out for! I went there 2 years ago so I don't know if anything has changed, but it's worth trying to give them a call I guess...