Hi there, I'm a 2012 applicant but took a detour to have a wee look here today
Don't worry about having left it too late, there is still plenty of time until the October 15th deadline, but I'd advise to have your application in a good few weeks before this just incase there's any last minute issues and then you have no time to sort it out. Also just as a general note of advice start your personal statement early and get it checked on the ps helper forum here, it's all private and the helpers are just that, SOOOO helpful. Oh and one last piece of general advice, make sure to write down all the hours you are doing (including dates) and keep notes, it'll make filling in any work experience forms and interviews so much easier.
Anyways, regarding work experience you're definitely on the right track. Farm work experience is very important, especially dairy and lambing, so stick with that dairy farmer until you have at least a week or two there. Make sure to book the lambing ASAP, find out exactly when the farmer will be lambing and try and get at least a week solid (it's not that far away and booking early is always helpful). 3 weeks is probably good for farm work if you're pushed for time.
Your plans for your vet shadowing sound good, I'd keep it at those 4 weeks unless you somehow have extra time during the summer. Someone said above to book an equine vet but I'd be tempted to think that the large animal practice will encompass equine work and so getting a further week there (rather than a small animal practice) if you have time would work.
The animal rescue centre sounds interesting and if it is mainly dogs and cats would count as kennels and cattery. Staying for the foreseeable future sounds like a plan and if you worked there for say the next 6months uninterrupted then you would have gained around 2weeks small animal work experience which is good.
The abattoir sounds like an interesting choice and would make your application stand out. It might be an idea to also get a day or two at a veterinary laboratory and/or something unique to your area or interests i.e. I'm very interested in wildlife so I spent a month in South Africa last year and also spent last Spring being involved in a local Osprey watch at a Scottish Wildlife Reserve. Other things could include pig farm, poultry, sea life sanctuary, aquarium, zoo or wildlife park etc. Aim for a week or so of "different", it'll open your eyes to new possibilities and really make your application stand out.
The only thing you haven't mentioned which is a
must is stable experience. Definitely aim for a couple of weeks if you can. If you have a riding stable locally then that's perfect, if not other things you could do is find a racing stable or trekking centre (it really depends on your area).
If you have a mixture of long term during your school term and short term using all your summer holidays there is every chance you can get over 10 weeks work experience before the deadline and that it can be made up from a large variety of placements.
If not, don't panic! I'm on a gap year atm due to not having enough experience the first time around and the past couple of years of applying and having a gap year have been fantastic!
Anyways, hope this helps, feel free to ask any questions and good luck!
Wow...didn't realise until after I saw it posted I'd written quite the essay lol