Thanks for your comments Mark. I tried replacing the thermocouple with a load cell and connecting the -ve signal to ground rather than pin 2 but I still get an output voltage which is about 80% of the supply voltage and which doesn't vary with adding weights to the load cell.
I'm not getting a lot of enlightenment from online resources. In other forums there are quite a few requests for help in amplifying small dc signals but no specific circuits offered to achieve it.
The main problem with trying educate yourself on the net is that the material has been written by experts (obviously) who have forgotten how ignorant newbies are and how simple they need to keep their explanations.
I think my best option is probably to see what courses are available at the local technical school and sign up for one.