For what it's worth, as far as I have been able to determine the following RAF / Commonwealth combat squadrons converted from Hurricanes to P-40s in the Western Desert (use of some types overlapped). It was a total of 7 combat squadrons in all:
From
239 Wing:
112 Sqn RAF (Hurricanes I in the first half of 41, Tomahawk in the second half, Kittyhawk I from Winter 41, Kittyhawk III in 1942, Kittyhawk IV in early 44, then Mustang III in late 44)
250 Sqn RAF (Hurricane I and IIB and IIC from February to April 42, Kittyhawk I and II April - October 42, Kittyhawk III from October 42, then Kittyhawk II again, then Kittyhawk IV in 44
, and finally Mustang III from August 45)
260 Sqn RAF (Hurricane I and II from Nov 41 - Feb 42, Tomahawk II from Feb - Mar 42, Kittyhawk I from Feb - Sep 42, Kittyhawk IIA from Jun 42 - May 43, Kittyhawk III from Dec 43-Mar 44, Mustang III from Apr 44- Aug 45)
3 Sqn RAAF (Gladiators and Gauntlets - and a few Lysanders- in 1940, then Hurricanes in 1941, then Tomahawks in late 1941, then Kittyhawks from 1942- Nov 1944, then Mustang IV)
450 Sqn RAAF (Hurricane from May-Dec 41, Kittyhawk I and Ia from Dec 41 - Sept 42, Kittyhawk III from Sept 42 - Oct 43, Kittyhawk IV from Oct 43 - Aug 45, Mustang III from May 45-Aug 45)
from
223 Wing
4 Sqn SAAF (Hurricanes from March 41 - plus some Mohawks - Tomahawks from Sept 41, Kittyhawks from some time in 42, then Spitfires in July 43)
2 Sqn SAAF (Gladiator and Gladiator II from 1940, Hurricane in early 1941, Tomahawk IIB June 41 - May 42, Kittyhawk I Apr 42 - June 43, Kittyhawk III, June 43 - July 43, Spitfire VC from July 43 - march 44, Spitfire IX from Feb 44 - July 45)
As far as I can tell, one unit,
239 Squadron RAF operating as a recon unit from England switched from Lysanders (Sep 40 - Jan 42) to Tomahawk I and IIa (from Jun 41 to May 42) to Hurricane I and IIc (from Jan 42- because they didn't like the Tomahawk). Then they were converted to the Fairey Battle in Jun 42!!! Then the Miles Master in March 42, then finally to Mustang I in May 42, and Beaufighters in Oct 43 and then Mosquitoes from Dec 43.
I couldn't find any Western Desert units that switched from P-40 to Hurricane
though I am not saying there weren't any. I just couldn't find it if there was.
5 Sqn SAAF never got Hurricanes to begin with (Mohawk Vk, Dec 41 with Tomahawk IIB, late 42 with Kittyhawk III, Kittyhawk IV in 1944)
In addition, some Canadian squadrons which seem to have been home-defense units based on Canada's Pacific coast, converted from Hurricanes to Kitythawks, but I don't consider these combat units. They included:
133 Squadron British Columbia (converted from Hurricanes to Kittyhawks in March 44, then to Mosquitoes)
135 Squadron Patricia Bay (converted from Hurricanes to Kittyhawks in May 44)
163 Squadron Sea Island (converted from Hurricanes to Kittyhawks in Oct 43)