Update.....
I have used another spool block, and the crane itself works fine, so no problems there.
The red valve, links the main inlet of the block to the outlet of the block ? also the handle was in the wrong position in relation to the position of the opening in the ball, this is now disconnected and the ports on the block caped off.
I have stripped the original spool block down, all spools are unworn and free to move, no chips or marks on them, using an air line at low pressure to test the block I get flow from main inlet of block to outlet side when all levers are in neutral ( centred position ). When a lever is operated the flow stops and does not exit through the actuator port ( A ) ! the other port ( B ) is vented to tank as you would expect, this is the same for all levers in all positions ? Agggghhhh whats going on.......
The centre spool with the extra block on the top of it as in the pic, I have removed and there are 2 inlets on the bottom, A and B and 2 outlets on the top A1 and B1, there is at each end of the block what looks like adjustable nuts, ( to adjust pressure ) ? but there is no flow through it from A to A1 or to B1 or B, and vice versa ?? using low pressure air line, what is this for and how does it work ? can someone explain ?
I will investigate more this week end if the rain stops......