Where are the 2-pdr portees? And in what strength? I.e., “they are in the AT Regiment, making up one of the batteries, while the other 2-3 batteries were towed.
Hopefully someone with considerably more expertise than me could take this on, but…
AFAIK, pretty much everything was in portee by the beginning of 1941 and remained so for all of the period you are thinking about. Infantry units were quite likely to be equipped with 25mm guns early on and I think they were en portee from very early on (their fragility was known about first).
The SP/towed division comes back in 1943 after experience with the 6pdr showed it wasn’t as handy for portee firing as the 2pdr, but was more robust for moving about towed.