Bartrop was advertising the Australian HD8 and the M8 models in the mid-1970s. They were certainly shown at the Royal Show and also the Institute of Groundsmanship Exhibition, both shows in 1975.
Trade reports state Bartrop saying that they imported the ride-on machines in kit form and then assembled them in the UK.
Bartrop detailed that the HD8 had a Honda G65 6.8 hp engine.
A few Greenfield HD8 and M8 ride-ons have come to light over the years, but they are indeed rare in the UK.