You can use the flat rate VAT scheme - there is a section specially for 'farmers' - not sure if it applies to smallholders too, but it does look like its geared to the smallholder and not farmers who spend massive amounts on outgoing VAT for plant, equipment and tata around the farm but can charge little in return.
http://www.hmrc.gov.uk/vat/start/schemes/flat-rate.htm#9But if I were you - less paperwork is good paperwork.
Even HMRC will give you conflicting advise depending on who you talk too and what day - no matter what business you run - they dont even know the rules - hence they are employed and not self employed.
Once you start treating your smallholding as a business for tax reasons - they may start to as well.
In the end it could be classed as your 'second job' and the tax on earning in a second job is quite big too.
If you wanted to start a Ltd company with your land you would also have to either charge your Ltd company money to rent your assests or sell your personal assest to your business.
If I were you - earn your wage - earn a bit on the side with your produce.