Early 80s would fit with the lack of tumble dry on the patterned courduroy dress, as this symbol was added to the list in 1985.
In the Laura Ashley book there is a quote from LA herself about how she never catered to current tastes and her customers were not those seeking high fashion but reminiscent and some what old fashioned styles.
The differences I have found between 80s and the 90s Laura Ashley are the waist shape - V shape and straight drop waist tends to be 80s, the 90s waist tends to be at the natural wast but straight across and a looser fit. I find 80s LA fit one size smaller than current sizes (excepting the drop waist styles) whereas the 90s examples are much the same sizing as today.