Dont know if it will help, but have emailed all the major horse feed brands (dengie, spillers, a&p etc) to ask if they can help out.
£2k is such a paultry amount for a large company!
I think Christmas walks or rides are a great idea, someone just needs to co-ordinate it in an area. I think you'd also need to contact EMW in advance to notify them of the event, so that anyone interested can confirm you're legit.
Someone on another forum thinks she can get some on-going corporate sponsorship. A few of them would be great, because it helps to secure the future of the charity, after we've met this appeal target. (Which we surely will!).