This is really bad 1v1 advice.
Taking fights all over the map means you lose fights all over the map, since equal cover IS will beat Volks, forcing you to retreat while he caps/decaps and pops medkit. A single volks won't be able to flank a Vickers. And against UC you need multiple squads to actually force it back. I'd recommend getting a rak as your next unit once you confirm UC, and not before. Getting a rak if there's no UC will put you way behind in the infantry game, contrary to what Katitof claims.
You literally HAVE to pair squads together vs Brits until you're on STGs. Volks don't have enough close range DPS to charge IS 1v1, but you lose badly at range. If you have 2 squads, you can take a bit of bleed to force him into hard retreats and secure map control.
4 IS + UC doesn't hurt the manpower for AT at all and certainly isn't considered spam - it is in fact a very standard build which is very manpower efficient since OKW will bleed terribly against it. 4 IS + UC will curbstomp you if you try to rush for Luchs, since you will get overrun and lose map control. And since AEC has the exact same timing as Luchs, you'll be doubly ruined. If I even go mech at all vs Brits I go Puma first before Luchs, but most of the time I just rely on MG34 + leigs to exploit their lack of smoke, lack of indirect fire, and lack of rocket artillery.
I've been able to use one Strum and a Kubel to take on single infantry units. It usually works pretty well although I lose 1-2 Strums when I do this.
Panzerfusiliers seem to hold their own. (So far.)