You can get the death cert from GRO. Tick Death Certificate, Overseas Events rather than the usual deaths, tick Yes you know the GRO Index and put in the year of death. When you get to the page where you put in his name etc. you will find there is only one space for the reference, you just put in the vol and page number and they should be able to find the certificate for you.
Lizzie
ps. That's what I did for my g.uncle's death certificate - he was killed in France in 1917. Cert arrived in the usual time, i.e. about 5 days.