The correct tactic in the desert really is to set up in a formation that allows you to fire into the German armour's flanks at 1000m or less.
German PzIII and IV have very thin side armour (3-4 cm) and even a 2 pounder can penetrate that to a reasonable extent to 1Km. 6 pounder and grant's 75mm to ranges over 1Km. The class 7 and 8 frontal armour can therefore be sidestepped.
So - probably work 2 units/formations of tanks along the top and bottom of the battlefield and get into flanking positions, with a smaller force held back centrally in overwatch behind the infantry advance.
If you engage a panzer and it turns to face your firer then immediately look at one of the other 2 tank formations to see if one of them now has a flank (to include turret side) shot and fire that - especially if that tank is already locked onto the target in question!. Rinse and repeat if the German turns his whole tank or turret to face current firer.
That technique works in the open battle, especially where the Germans are advancing. It can be made to work in an attack, by selecting one objective area and taking and holding that and then waiting for the counter attack, with the tanks set up to flank that (you will usually know where his tanks are by then especially if you have air recce). In the attack, blow your way to an objective cluster with massed arty, relying mainly on the infantry to lead behind the creeping barrage. Don't be subtle.
You have the Lee/Grant. That can occasionally ping the class 7 frontal armour at about 750-100m. However, his long 50mmL60 sabot can get through your class 6 frontal armour on occasion too. So sit up on a higher elevation than him, and you will be classed as
hull down therefore receiving less hull hits and more front turret as well as a slightly more difficult target to hit. Your little turret has class 10 armour.
Also - ensure that you bought the Lee/Grant that comes with more AP ammo. (There are ones with a bias to HE). The 37mm is rather less effective in AP than the 2pdr (which was one of the hottest in the 37/40mm class). You can also use the bren gun carrier ammo carrier version to hide behind a ridge and supply a tank up on the ridge with more ammo.
You have the 6 pounder ATG - that will slaughter the panzers from the side to 1500m or so. It will do them frontally at 5-600m as well. I tend to have 6 pounders towed by half-tracks or bren carriers, and set these up behind a hill, or on the back of a plateau where the Germans will present themselves at 300M or less. Sprinkle infantry out front to look out for dismounts. Lose any 2 pounder ATG - worthless except against light armour by then, unless in a short range flank ambush. Upgrade is only a few points so why keep them when the 6 pdr arrived?.
AI armour will often carry tank riders - so use your arty and mortars to hose down any spotted AFV. Especially, use mobile (15cwt truck will do) Vickers MMG as tank delousers. If a section falls off an AFV - then fire at that and let the area effect ping any neighbouring sections or tanks which may still have riders (and which may bot be in the MMGs LOS). Move the MMG teams as and when too much enemy attention arises (deploy with a slope behind them - they can withdraw out of LOS for vehicle pick up and redeployment).
As to arty - the + batteries of 25pdr I tend to avoid in the core. Rather too expensive IMHO, and I usually only run out of regular HE in an assault or advance when the game is already won. For the points of 2 (+) troops, you could likely have had 3 regular, and to me the extra troop is more use.
In the advance or assault - find the German armour and drench with 25pdr. If you find a platoon position then give it a battery plus of fire (2 troops) and walk the shells over these tanks for 3-4 turns. Adjust fire one hop if necessary when it has fallen to concentrate on a spotted tank.
There is no note of a core forward observer. A core FOO is
absolutely vital for any army, but especially for an artillery-oriented army like the UK. He will gain experience and so will the core arty, resulting in very quick calls for fire eventually.
Sherman is about to arrive - until the end of Tunisa these are very useful tanks if the German does not have the long 75. They walk over all panzer 3 and short-barrel Mk 4. Churchills also will arrive by el Alamein - some like them, others think they are too slow.
When the Germans have the upper ATK hand - especially when long 75mm tank guns start being regular appearances - then you want to spot these things and if you cannot plink them off from a side aspect with direct fires, then drop the arty hammer on them. In the early days, the 75mm Mk4 'specials' are a rarity - and a prime target to plink at long range with your grant 75mm, as the front turret is only 5cm, so being hull down is actually a disadvantage for them..
Towed 17pdr will arrive eventually - but not worth getting IMHO. Maybe one section, but ensure they have half-track transport. Like the German 88s, they are large and obvious. Tigers are usually not spotted in numbers till Italy - a few in Tunisia maybe. If seen, direct all available arty onto these until they are reduced to a small pile of nuts and bolts.
German Nebelwerfers if they appear can be a pain - direct expert 81mm mortars (captured Italian should have the range, else 25pdr) onto those and work over the big smoke puffs they leave. if a human opponent - even more need to deal with (he will reload them, unlike the AI!

).
In a nutshell:
Don't head-butt against German armour in WW2, work around their flanks. Only Tiger has decent side armour.
USA/UK/Soviet - you have the artillery advantage in real life, so
don't forget that. Hammer any annoying armour with the field arty - all of it servicing the one platoon at a time, preferably, mortars reserved for the infantry. Any large pack of panzers seen especially advancing - is a prime target (tank riders).
Cheers
Andy