I don't want to steal Harribobs thunder (I'm sure he'll come back later to confirm or shout me down

) but I'll say
BMF - British Mediterranean Force
18/3 Bde - 18 Battery, 3rd Brigade, RA (artillery were organised into batteries and brigades rather than say companies and battalions)
Supry - supernumerary
3e - third (though why written with the French abbreviation rather than 3rd I don't know)