According to the Commonwealth War Graves Commission Private Corkhill lived until 29 May 1940. No known grave. His name is inscribed on the Dunkirk Memorial. Richard Annand VC and Private Corkhill were both in the 2nd Battallion DLI.
It's a bit long but from his citation in the London Gazette are the exploits of Richard Annand VC. The circumstances will be similar for all near the River Dyle that day.
"For most conspicuous gallantry on the 15th-16th May 1940, when the platoon under his command was on the south side of the River Dyle, astride a blown bridge. During the night a strong attack was beaten off, but about 11 a.m. the enemy again launched a violent attack and pushed forward a bridging party into the sunken bottom of the river. Second Lieutenant Annand attacked this party, but when ammunition ran out he went forward himself over open ground, with total disregard for enemy mortar and machine-gun fire. Reaching the top of the bridge, he drove out the party below, inflicting over twenty casualties with hand grenades. Having been wounded he rejoined his platoon, had his wound dressed, and then carried on in command. Richard Annand's platoon sergeant said later "Mr Annand came to me at platoon headquarters and asked for a box of grenades as they could hear Jerry trying to repair the bridge. Off he went and he sure must have given them a lovely time because it wasn't a great while before he was back for more. During the evening another attack was launched and again Second Lieutenant Annand went forward with hand grenades and inflicted heavy casualties on the enemy. When the order to withdraw was received, he withdrew his platoon, but learning on the way back that his batman was wounded and had been left behind, he returned at once to the former position and brought him back in a wheelbarrow, before losing consciousness as the result of wounds".