Thanks for those links, Andrew. Made some progress with the suggestion
make modules
make modules_install
Running
sh NVIDIA-Linux-x86-1.0-5336-pkg1.run --kernel-source-path=/usr/src/linux
now builds a kernel module, but then fails with the error
Unable to load the kernel module nvidia.ko. This is most likely because the kernel module was built using the wrong kernel source files. Please make sure you have installed the kernel source files for your kernel. If you know the correct kernel source files are installed you may specifythe kernel source path with the '--kernel-source-path' command line option.
I seem to be going round in circles ....