Give us your changes (if any) for the forementioned units as a starting point, and we can talk.
Imo the changes to UKF infantry are not enough since they can still equip Bren and Vickers or Bren and Piat and are still powerful in cover and weak on the move.
It might be worth to try the following suggestions :
1) Change bren from LMG to an "assault rifle" allowing to fire on move.
That would also be historical more accurate, since in real life bren is closer to bar than an LMG-42.
Reason: better synergy with both tommies and R.eng and allowing to change the role of tommies to from static defensive unit to more mobile unit.
2) Cover bonuses and penalties now apply only to lee Enfields. (point blank DPS of Lee Enfeilds should probably go down a bit.)
3) Bren DPS curves makes it strong at mid/close weak at long range, doubled equipped is allowed price goes down to 30-40.
Basically buying brens reduces the units long range DPS in cover but increases the DPS on the move and out of cover allowing player to modify the behavior of the unit.
4)Vickers K remains an LMG with it live DPS but its available only doctrinal in the S.W.R. . In addition the Resupply truck ability is scrapped with vickers K available either from base or from Forward Assembly.
Heavy Sappers upgrade:
Has no movement penalty
gives +1 armor so sapper take less damage when repairing underfire
increase squad size +1 so that they can increase with better speed but at the cost of more pop
replaces stens with lee Enfield so they do not become too good as close range unit.