From what I understand picking up "casual labor" in London = finding a desperate American looking to work for the summer.
Guess it's the same world 'round?
Anyway back to the TOPIC....
Try the circuit (for testing purposes only) without the GFI and test for current.
No current.... Try a new GFI.
If all else fails, cut the power, grab the wire and aggressively rip it out of the ground. This will loosen the soil plenty for its replacement. (Without the casual labor)