By Julia Banim & Charlotte McIntyre Jonnie Irwin, who has died at the age of 50 following a cancer battle, once urged people ‘to learn’ from his ‘mistake’ that he came to regret in his final months. The Channel 4 presenter’s death was today announced by his heartbroken wife Jessica Holmes, with whom he’d welcomed three children Rex, four, and twins Rafa and Cormac, three. Taking to Instagram with the devastating update, Jessica wrote: “It is with heavy hearts that we share the news of Jonnie’s passing. A truly remarkable soul, he fought bravely against cancer with unwavering strength and coura…