Hard choice.
First choice, Royal Marines.
Second choice, Royal Armoured Corps.
Third choice, Any of the British Army research establishments (especially tanks) so I could play with everyone else's tanks, guns etc. during and after the war.
___________________
"The Fuhrer believes the troops have not fought as the situation demanded and orders the SS Divisions to be stripped of their armbands" Field Marshal Keitel to Sepp Dietrich, March,1945