there are a few places you can try these two is where a i have been getting some bits for mine recently, Cox and Turner, is the first they are usealy at dorset as well they have a web sit but it's still in the middle of being put to geather this is there ebay shop
http://stores.shop.ebay.co.uk/Cox-an...__W0QQ_armrsZ1
and you could also try Cotswold Vintage Tractors loads of stuff lots of second hand bits
http://www.cotswoldvintagetractors.com/fordson/home.php
there are others about there are just the two i have been useing