Roderick Grant (I think he’s Hugh Grant's dad) wrote a good book on the 51st HD in WW2. He was intelligence officer.

In that book, photos of pipers of the BW can be seen wearing their Royal Stewart kilts playing to wounded comrades in the Western Desert in 1942.

There is also an excellent portrait of Piper Dawson, in his KD with kilt.

Did they dress up for the photos/portrait or were they wearing their kilts throughout ?

For sure, Highland pipers and Highland Jocks in general donned their kilts at the slightest provocation !

Examples from memory include the 2nd Gordons newly off the boat and in their kilts lining the route of the Japanese victory parade in Singapore February 1942. The survivors of the battling Argylls and Royal Marines (Plymouth Argylls) rode past them in some recovered Argylls’ trucks.

The 51st HD parades in Tripoli and later in Tunis 1943. They were a main part of the victory celebration, as the massed pipe bands went swinging by in their kilts.

The 51st HD entry into St Valery-en-Caux, September 1944. Field Marshal Montgomery changed his order of battle so that the 51st could liberate the town. The pipe band wore their kilts of course.

Captain Ogilvie of the Glider Pilot Regiment who wore his kilt, para-bowler and BD blouse throughout the battle for Arnhem, September 1944.

The Pipe Band of the 7th Argylls of the 51st parading through Bremerhaven, May 1945, kilted, to the bemusement of the collection of senior German officers they passed by.