Where do I start??

[Northerngeezer]

Can anyone give me any tips on where to start regarding a relatives service record?
I have a name, DOB and a place of birth, nothing more.
Also, I'm looking for my fathers national service record, he's still alive but is unable to give me any information due to Dementia.
I'm assuming rightly or wrongly that he would have been conscripted at the age of 18, so that would have been in 1951.