Hi Everyone,
To wrap this thread up I have solved all the problems with running Squeak using GPIO ports on raspbian-stretch-lite. To get the latest Squeak Scratch:
sudo apt-get install nuscratch
To get Squeak to use/find the GPIO stuff I added symbolic links to the folder where the Squeak VM lives that point to two .so files:
/usr/lib/libpigpio.so /usr/lib/libpigpiod_if2.so
Many thanks to Tim and Dave for their help.
Lou