Awesome thanks for that. Did the oil and filter no problems. Swapped out 3 spark plugs then snapped the last one off in there. Only the thread left. Disaster!
There are specialist bolt/plug removal tools like "easy out" which may help. Used to be a very common problem with Ford cast iron heads at one time. It depends on what's left of the plug in the head, whether it seized or badly cross threaded [ bad news] This is a job where experience is paramount- knowing when and how to apply brute force and when to wait for penetrating oil to work and which tool to use and actually possessing one! Time to visit your local engine rebuilder or a local garage with experienced motor engineers I think