Help to research my Grandad at Dunkirk (Possibly Irish Fusiliers)

Depending on where you live you can obtain a copy of the death certificate online from your records office. Links here.
Where to go for birth, marriage and death certificates - The National Archives

A photocopy of the certificate is acceptable.

I git round the fees by applying on behalf of my mum and gran as they were higher up the next of kin ladder than me!