AndyT,
Many garden appliance workshops do have the tools needed to check your carb on following issues:
1) sound membranes (should be OK in new engine)
2) carb will pop-off when pressure is applied.
3) carb will hold fuel pressure without dropping when engine is steady(stopped)
4) Bumping the prop to and fro against compression will show a slight drop in the applied fuel pressure at each bump, indicating that the carb works.
5) checks of fulcrum height for the fuel chamber needle lever.

Add to that, meticulous checks for any foreign matter anywhere inside the carb.