More gospel according to Ronnie...
Due to low demand, of the 20 chassis assembled for the MkIII production run only 7 were actually then built into MkIIIs, M3/1101..M3/1107. The remaining 13 were either built up in period as "late production" cars (P/1080, P/1081, P/1082, P/1083, P/1085, P/1086) or sold as post production chassis (which Ronnie and Willment retrospectively gave numbers P/1108, P/1109, P/1110, P/1111, P/1112, P/1113, P/1114). P/1110 and P/1111 were used as replacement chassis for P/1012 and P/1078 respectively (though P/1012's original tub was later resuscitated as well!). P/1108, P/1109, P/1112, P/1113, and P/1114 were built into new cars.