I have a 2005 Aero S2 and a 2013 Aero Coupe. They both have great big dinner plate front discs and despite a low weight and medium sized front contact patch I have never had them lock up. I have had times when I have pressed hard, also in the wet, but never had a lockup?
They are exceptionally good brakes.
I would be interested if the issue is old/worn rubber. My experience is that the mileage tends to be low per annum. The car does not punish its tyres due to lightweight and non-psycho driving manner normally found in Morgan drivers (even Aeros). This will often lead to the tyres becoming more hardened with age which would lead to increased skid risk?
Now let's not talk about the handbrake on the S2.
- if it's anything like the S1 Aero Alistair,it begs the question
'what handbrake....?' 
James