They are mostly Oxfords, Volvo & Scania, if they are curtain sides, I removed them to get the flat trailer. Lido do some suitable one as well, again removing the 'box' on the back.
Dave,
The fencing is Knightwing, see
http://www.knightwing.co.uk/cgi-bin/commerce.cgi?cart_id=1408200813.118&product=OO-HO_Building_Kits&pid=242