Our abattoir (STM, Henfield, West Sussex) salted it shortly after skinning it, and we collected it the next day. They are allowed to release them to you provided that the cattle came from you, and provided that you will be sending it on to a licensed entity for finishing the tanning process after you have salted it for a couple of weeks.
We investigated it, and there are limited people that carry out the process. First it needs to go up to Holmes Hall, and then it gets sent down to Pittards in Exeter. You will need to get a number from Pittards, and they will charge for their work and the Holmes Hall work. For a Dexter hide the price is £149 plus VAT. The chap at Pittards is very very helpful - Robert Painter - 01935 474 321. If you contact him, he will email you an explanation of how to do the initial curing with salt, and answer all your questions.