Fact.
The problem with most brake / size issues are usually either brake fade due to overheating and glazing which can be extremely rapid and dangerous if brakes are really not adequate - or the worst one, lack of progression. What this means is that you CAN lock the brakes given enough pressure, but you cannot really control the actual braking progression, it is a sort of all or nothing - well, quite a bit of all, quite a bit of lock, and nothing in the middle really. These are the usual signs that brakes are undersized.
Again, on the L series, I do not believe these is either of the above - purely a lack of power assist. - Answer is to fit the larger and more efficient servo - not larger brakes as the larger brakes are not needed and will not improve the braking performance..
I fully agree that when using an auto box the brake usage is higher due to less engine braking. I also agree that anything that one can do to improve brakes is good. What I do not subscribe to is that the L series - or indeed any Mk 1 NEEDS larger brakes - again it simply needs more power assist. When working correctly (which many times they are not the L series brakes are quite good and more than adequate - simply heavy.
I agree that there is a lack of servo assistance, even on the later servo. However on the testing I did on my V6 brakes. I found them under sized for the job in hand. After just 2 hard stops from 70 Mph, the front discs showed a temperature of over 250°C!! While this isn't in the danger area for the pads. It is hotter than I'd like to see, and definitely has a smaller safety margin. My MG ZS180 with its slightly larger brakes showed just 160° C after two identical stops.
The thing with auto transmission gearboxes isn't just reduced engine braking. There's a lot of transmission "push" under braking. If I'm slowing down gently on the brakes of my auto, I can feel the engine pushing the vehicle against the brakes. If I put the transmission in N and repeat the test. It'll stop in half the distance with the same pedal pressure. Or it'll stop in the same distance at half the pedal effort. So the auto definitely needs the extra brakes fitted from the 2000 update.