Like Tim, I was waiting for a Snetterton expert to chime in. The name Philip Heseltine is surprisingly unusual, with very few hits on Ancestry in England.
I've found two Lieutenant-Commander Philip Heseltines on Ancestry - probably father and son. The elder one - who is likely your man - was Philip Edward Heseltine, born August 27th 1904 in Hull, died 1992 in Bury St Edmunds. He was presumably a 'career man' as he's in the Navy List between 1924 and 1949 - a full 25-year hitch - although he appears to have not been promoted after 1934, so possibly on the reserve list. [edit: or maybe, like Ian Fleming's Commander Bond, he was doing something more 'interesting'?]
The second Philip Heseltine arrives in 1935 as a 6-week-old baby on a ship from Malta - the Bendigo - and many of the others who had boarded there appear (not surprisingly) to be members of RN families - lots of home addresses around Plymouth and Portsmouth.
If it's the right chap - and believe it is - then his full name was Philip James Heseltine and he was born on July 24th 1935 (presumably in Malta?) and died in Plymouth in 2002. According to the Navy List he was an engineering officer, commissioned as an acting Sub-Lieutenant in September 1955: the last Navy List on Ancestry which mentions him is Spring 1968 - by which time he was a Lieutenant-Commander, a rank he achieved in November 1965. He married a Susan Tremeer in Plymouth in early 1960: I'd guess she was probably another 'navy brat' since I can't trace her birth either, although there were a couple of naval officers with that unusual (Cornish?) surname in the mid-1950s..