However, the wing strengtheners were intended for the weaker A/B wing not the stronger universal wing, though they are also present on the restored example.

That’s popular belief, but in fact they were also seen on C-winged Spitfires (including Mk IXs).

12 exhausts were fairly common but there are plenty of LF Mk.Vs without them.

Plenty? Are you not thinking of non-LF Mk Vs with clipped wings?

According to my files the only Polish pilot with roughly maching name and a Mosquito score was Sgt Kazimierz Leszkiewicz (780887) who destroyed a Ju88 on the ground at Husum on 25 April 1945.

As regards the Polish Mosquitoes at Exeter question, here is No. 307 Sqn Mosquito NF.II HJ932 EW-L photographed (in fact filmed) in colour at Exeter on 28 March 1943. F/Lt Jerzy Damsz (left) had just brough F/Lt Hugo Hrbacek (right) to base. Hrbacek, a Czech Spitfire pilot was downed into the Channel that day. When he was picked up, Damsz flew in his Mosquito to Tangmere and brought him back to Exeter.

A different kind of white-and-red chequer motif.

Une belle vue, aussi.

different type in color and flying

What an ugly thing!
This North American fighter looks much, much better.

Another Hawker with black-white chequer motif.
Photo courtesy Historic Aircraft Collection.