@AvrilG Living in Ashington makes things a lot easier for you! Pop along to the Northumberland Archives at Woodhorn. I'm pretty certain that they will have taken care of the parish records from St Peters (West Sleekburn). You can find their opening hours at
https://www.northumberlandarchives.com/.
I don't think you need to book before visiting. They can do a search for Edward’s grave, verify which cemetery and give you the plot number of his grave.
I forgot to mention that St Peters (West Sleekurn) got a new cemetery when the original was full. It is located next door to the Forresters Arms on Wansbeck Terrace in West Sleekburn, and just opposite the site of the old St Peters church and cemetery. Just when it was opened, I can't be sure but it is registered by the Commonwealth War Graves Commission as having a few war graves from WW1 so it was there at the time of Edward's death. It might be worth having a wander round the gravestones to see if any names ring a bell.