By the style of the battledress,seems to be after 1945,and possibly Canadian.
Can't understand why there is no Regtimental shoulder flash the arm badge could be the Catterick Rose.The despatch rider could fit in with Catterick it was the home of the Royal Signals.
You can get his whole army service from army records it's now in Scotland,you need to prove who you are,and the search fee up front is £30.the Royal Navy do it for free.