I agree with you about proper manuals.
I have collected the following manuals, some on DVD:
AKM 4935 – 9th edition – 1976 (paper copy)
AKM 6353 – 1989
AKM 6353 – 2nd edition - 1991 (paper copy)
AKM 7169 - 1992
RCL 0193 – Mpi supplement - 1996
Apart from the earlier editions of AKM 4935 and also AKM 6799 (the Spi supplement of 1991, superseded by AKM 7169) this is a complete set.
AKM 6353 covers all Minis from 1976 to 1989. The second edition includes the RSP and Mainstream Coopers.
Actually there was no big change to the Mini in 1976. AKM 4935 must have continued to be used until 1989 when AKM 6353 was published.
The A+ engine was introduced in 1980 and yet AKM 6353 makes no distinction. For example the 1275GT had the A engine and the ERA Turbo, RSP and Mainstream Coopers had A+. The manual just refers to the 1275. Though if it was published in 1989 I am sure it must be more focused on the A+. I suspect the differences in workshop terms are not significant.