For the record, there is this site
https://www.deceasedonline.com/servlet/GSDOSearch
It doesn't include every cemetery and crematorium, but more are being added all the time. i have looked for Edward Dennis, but nothing came up. This eliminates from your search all those establishments that are included if you care to peruse the list.
I then had a quick nosey at this family and if I have the correct one, Edward's father was Arthur (1886 - 1928) and his burial came up at Brompton Cemetery - the link above is for Arthur's record. You buy credits to see the burial register scan / map of grave location.
No matter if I have the wrong family, it's as good example as any other to start exploring the site!