The Brew Cabin

My front garden is 4.5m square and I am planning to divide it into 4 triangular borders with 2 diagonal paths about 500mm wide, (the paths will only be used to tend the borders). I intend to use Tegula block paving with rope top edging. Having read the pages on block paving does this type of path require 200mm of hardcore and 50mm of sand as a sub-base and concrete haunching for the edging or, considering the level of usage, can I use something less substantial?

75-100mm of sub-base material is adequate for your garden path. 200mm is OTT and I think you've proabably misread the web-page, as the usual recommendation for residential use is 100mm minimum.

Given that it is such a small project, with no vehicular traffic and very narrow paths, you could actually get away with laying everything on a 75-100mm bed of concrete, or the 10:1 bedding mix I espouse for patio paving.