Creda Tumble Dryer 37747. No Heat?

Hi

Taking advice from previous posts on this subject, I tried the paper-clip trick on the left thermostat. It gave a loud click so I presumed it had reset successfully. However, still no heat.
Other answers mention that 9 times out of 10 the thermostats are to blame for this. So I ordered a new set and fitted them today. Still no heat.
I measured the heater elements and both are around 21 ohms. I then followed the wires back towards the switch, but they connect to a block on the bottom of the dryer, near the motor. Is this a relay? Could it be faulty, or am I overlooking something more obvious.

Thanks
Ernie