If you're not old enough to remember when these books were filed along a shelf in every decent Garage, they listed the service data for every vehicle the average garage may get asked to service - every model current in the year of publication, from data submitted by the manufacturers. Updates were published annually up til the late 1980s. After that, Glass's published a less reliable version for a few years, by which time it was all becoming available online. Below are some excerpts for Reliants:
The Rialto2, with the high-ratio rear axle does not appear, but the only other data difference is for the HT-E engine found in the 2, - the figures for this are given in the 1983 data above.