There's no denying that the Brits have a strong late game thanks to their excellent tanks; and they are invaluable to have to team matches thanks to their good tanks and strong ability to support their allies with emplacements and defensive infantry.
But in 1v1 matches the Brits, right now, are horribly outclassed in the early-mid game. From what I can tell playing 1v1 as the Brits, this is for a few reasons.
1) The British rely far too heavily on the mortar pit to help them win the early engagements: In nearly every situation I've played the early game British infantry cannot out-trade the Wehrmacht or Oberkommando infantry when in the same level of cover as them so they need a mortar pit to help win the fights (or a sniper, but snipers are only useful on certain maps), only the mortar pit is so easily countered by German mortars or ISGs that it dies too quickly. I've found UKF getting beaten by infantry blobs of Grens / Volks in the mid-game because of this.
2) The British have no snares: "But" I here you say "if they go special weapons regiment they get AT Infantry Sections". Well yes... that's one snare, locked behind one commander, and honestly not an especially good commander compared to Vanguard or Infiltration. This leaves the British incredibly vulnerable to light vehicle play (which can also deal with the mortar pit by the way unless you go 2 AT guns, which in turn limits your ability to deal with massed infantry). This leads me to my third point...
3) The British have no good mid-game mobile anti-infantry: The Centaur has been rendered next to useless in past patches. It's slow and lacks armour and by the time it comes out the German faction probably already has a Panzer IV or some other tank out on the field. It's no wonder it's never seen anymore when the Cromwell is a far superior choice.
Long story short if Relic wants to make UKF viable in 1v1 again some serious changes will have to be made to the faction.
My suggestions would be this:
Are my suggestions good ones? No idea, I'm no game designer or modder, just someone who wants to see the Brits be fun to play again in 1v1.