They're pretty cheap to buy new - I don't imagine its worth trying to repair them.
We have second hand trolleys and shelves for sale (not CC obviously!) - 12 bases with uprights, 26 shelves, excellent condition, but no longer required; pm me if interested.
A bit to far away for me.
I have repaired stuff for local garden centres in the past.
Thanks for your replies guys. I have recently acquired these trolleys, so don't need to buy any more. Wish I'd known about your trolleys Nick as I might have gone for those instead.