Thanks guys. I also tried AI and got a slightly different answer:

"The Morgan Motor Company sourced the front brake discs for the Aero 8 Series 3 directly from AP Racing.The technical breakdown of the front brakes for this specific generation includes:OEM Supplier: AP Racing (based in Coventry, UK).Morgan Part Numbers: MBS00156 (Front Right) and MBS00157 (Front Left).AP Racing Cross-Reference Part: CP7077-108P.Specifications: 348mm diameter x 32mm thickness, cast iron ventilated discs, paired with 6-piston AP Racing aluminium callipers."

Interestingly I tried to get prices from two different Morgan agents for these part numbers. One quoted £300 per disc and the other £750 (!)

I cannot for the earth of me think why Morgan would not use an off-the-shelf disc so I'm going to keep looking... will let you know how I get on.

Am using the following updated dimensions:

348 Dia
70mm centre hole
32mm thickness
42mm offset

Mulfab have offered to make up a set too (they make S1 and S2 but not S3 discs) so I'm going to take them an old disc tomorrow to check measurements and get a price.

1983 + 8
1978 + 8 DHC
1959 + 4 DHC
1959 + 4
1953 + 4 Interim
1953 + 4 flatty
1952 +4 flatty DHC