Due to other issues I have not been able to post for some time so was unable to comment at the start, but I have been keeping track.
I have used both weapons extensively with the SA80 coming in about half way through my career. I have not used the A2.
Some points
Left handed shooting was never taught as a conventional skill with the SLR, it only came in as a result of NI. Observing from the left of cover was taught but not shooting. Within the op banner trg package (I took part in quite a number and was safety on a lot) left shooting was taught and practised but only so that the soldier was confident in aiming and firing. Targets were set at 100m and no record of score was kept. It was discovered after about 4 years of op banner that soldiers werer not hitting the enemy and “shoot to kill” was publish in about 75. It was found that shots fired to hits was about the same as those in Tangiers in 1665. This also led to SUSAT being introduced and other types of aiming aid. Firing from the left hand was never practised out side of NI because the trg ammo was not available and range time was very limited. Most time you had one range day with zero in the morning and APET in the afternoon or zero before on the 25m then APWT. I have spent most of a two day range package reteaching soldiers to group before they could zero and fire the APWT. The best you could say about left handed shooting is that it would keep their heads down and look threatening as you observed round a corner.
I liked my SLR and I was a competent shot firing at Bisley in 77. but you must look at it as a weapon system not just the rifle. Stick a bayonet on the end and your performance went down hill quickly. It was heavy although after 6 month walking the streets you got used to it. Some found it difficult to shoot particularly shorter soldiers and gun shy was a real problem. The ammo was very heavy with front line scales of 80 rds +50 link/bandoleer at about 6 pounds.
Although the SA80 was just lighter than the SLR the weight was all to the butt. This made it easier to carry for long periods particularly with the sling. With the butt in the shoulder the weight was in your body and supported by your right elbow. The left arm had to contend with very little weight and was free to move and support the rifle rather than take the weight. You could almost fire one handed. You could now carry far more ammo. The introduction of what is all but a pare of binos to every infantryman cannot be underestimated. It meant that you were observing with your rifle not with it to one side. The eye is slightly higher and this did cause a number of problems with muzzle clearance.
The change lever being at the back was brought up when the weapon was on its way round to as part of the info tour in 80/81. This was explained that to move it forward would cause a complication in the operation and I never found it a great problem. I never had a problem with the safety catch but then my rifle came to me first and not 10 years down the line. As for putting it off in a hurry, as my finger would normally be in that position, not on the trigger, with the SLR there was never an issue. The cocking of the rifle again was not a problem, same as the SMG. And as I would normally make ready as I was heading for cover it was the same action just that now I would tilt the rifle to the left instead to the right as I cocked.
The mag release catch was an issue which was pointed out as soon as it reached my Bn. We were the first Bn to use the weapon on ops and it became quite clear very quickly that there was a problem. Our armourer designed, made and fitted (with araldite) the shroud around the release catch. This solved most of the problems but not all and so soldier would attach cord between the mag and the rifle so that they would not loose the mag is it came off. I think the locating of the release catch had more to do with a job lot of Colt mags than any thing else.
Lots of the problems that are associated with the A1 I never encountered. This may have more to do with my rifle being new then the design. I had one for 14 years and it worked very well with no discernable difference to the number of stoppages then the SLR.
As for the bullpup system, until you have had to run around leaping in and out of vehicles, through windows, crawling through the undergrowth and generally carrying a rifle 24hrs a day you cannot comprehend the difference that a shorter rifle makes. For a long time I could not understand why I saw photos of US soldiers with the butt of the M4 over the shoulder and aiming. It was then explained that they do it to shorten the rifle in house entry. May be the need for a bullpup has been seen?
The only real thing people have against he SA80 system is that you cannot fire left handed, so what, they never could with the SLR.
Given a chose, and I have thought long and hard about this, I would pick the SA80 weapon system over the SLR.