£1300 is a lot of money to spend to mess about in fields!!
better to check the scrap yards an classifieds for something that needs atention.
when I had a bike before (like the one in the picture I linked), it was £50 second hand from someone who wanted rid of it.
Had simillar deals on road bikes that I've taken off road as well (though these don't last nearly as long as off road bikes when actually off road).