Ex wife won’t help support our son

My wife and I divorced 6 years ago. It was agreed that our son, then 10, should live with his mother. As he was to live with her and as I was depressed and in denial about our break up, I allowed my ex all the proceeds of the sale of our home and tried to start again with very little. Soon after, I was diagnosed with throat cancer which reduced my income substantially. However, within a short period of time, our son was living more with me than with her as he couldn’t get on with her boyfriend. Within 12 months, he came to live with me permanently. I have supported us from my income as a club manager and more recently as a company rep. never asking her to contribute. I survived the cancer but received a terminal illness payment which I used as a deposit on a small house for us both. I have a £100,000 interest only mortgage However, I recently lost my job and, as I am 65 next month and will be living off my state pension, approached my ex for a little help with our son’s expenses. She flatly refused although she is a partner in several pubs and has this year bought property in both Spain and France!

She has substantial income and boasts stocks and shares investments (her partner is an ex-banker). I have no partner (nor have since the divorce) At the moment I receive benifits and do have a little savings which will be gone within 12 months. Please Advise what course of action I should take.