One year later!
I imagine the OP has probably solved his problem by now,
Max.

 

Hi Max. I haven't solved the problem exactly but my good lady doesn't have any restoration projects at the moment so it has temporarily solved itself. Peace in the man shed. Thanks for your useful comments.

@Papabravo - no MI suffered (humour). Why would I worry about that anyway? I had CA Bronchus (May 2018) which responded well to chemo- and radio-therapy and remains in remission. Now I have ? mets on my L adrenal or possibly pheochromocytoma - under investigation. Get all that? I worked as a biomedical scientist in the NHS and Philips Electronics for 28 years. (No humour.) What is your professional background within health care?

 

@MaxHeadRoom - Like your tagline. I use this one on other forums (esp. Microsoft ones):
"We cannot solve our problems with the same thinking we used when we created them."
Albert Einstein

 

Insert a line voltage timing relay, warning device and correctly sized contactor between the pressure switch and motor. Supply a suitable enclosure.

Do you need a ladder diagram?

 

Many thanks to all who have posted solutions. Many of the solutions involve components (e.g. timing relays) which cost nearly as much as the compressor. I'll simply put it outside the garage next time my good lady is using it while I am in there and hope it doesn't upset the neighbours too much. Thanks again.