I didn't think unsecured loans would be large enough to purchase land these days.
Have you tried AMC or just a presonal loan from your own bank? Could someone be guarantor, or could the vendor offer a private mortgage?
There was a company sprouted up recently offering farmland finance, it was discussed on British Farming Forum, its name seemed to suggest it was affiliated to the Nationwide Building Society but it is not, general consensus was avoid avoid avoid!!
Good luck, please let us know how you get on