SSD:- this answers your question on where the TAT probes were located. Strictly, you don't need temperature to calculate Mach as it is independent of temperature when expressed in EAS (or CAS) terms.
Shane:
The "crown modifications" were external straps to be applied to the upper part of the fuselage to extend its life in those areas which had been designed to safe life concepts - basically the Aerospatiale bits since BAe designed their bits according to damage tolerance rules. It wasn't a small job, but I'm afraid I can't tell you how many aircraft were modified.