Hi,
As we're not activly farming at the moment and all the business stuff is still delt with by my dad I can't really give you much advice.
But I'd assume if you registered as a business you'd then have to keep accounts, pay tax & NI etc it may also open a can of worms with planning
who could then ask for business plans showing financial viability, impose restrictions on use of buildings etc
It's my understanding (but again, I might be wrong) that unless you make more than £1000 profit in a year you don't need to register for tax & vat.
If you've got a friendly, local accountant it's probably best to have a quick word with them.
Hope that's of some help.
Karen