Looking for info on service record

HI , I am looking for information on what my grandfather did in second world war. I dont really know where to start other than i have searched on forces web sites and his name is not showing on any of them. I know he was in the royal marines
i know he served in burma and was one of the first on site when they liberated Changi Jail in Singapor. I also beleive he was with Montgomery at some point some where but this was always skipped over when he did speak about the war on the rare occasions he did. could anyone tell me where to start or why he is not showing anywhere
Thanks

 

No I have not , i did not know there was one of those , i will have a look I am guessing that they have records of service persons? Do you know what i would have to give them? I do not know his service number only his name DOB and so on?
Many Thanks

 

I have looked on all of the websites for the records but no not the MOD itself. Would there be a specif department do you know ? or just the general helpdesk type email ?
Thanks

 

Thank you I will need to get my mother to approve it by reading that as she would have been his next of kin but he died 5 years so i dont have his service number either i might give them a call and see what is the best options for me.
Is it normal or common for a persons record to be missing or not show any record of them at all

 

Thank you all for your help. I will look through all of the details and info of these sites and fingers crossed mufht get some luck