Hair canvas,is usually known as dressmakers canvas/hair canvas/jacket interfacing.... it's readily available here from places like John Lewis. it comes in narrow widths.
It's not be confused with the vilene type of interfacing.
As stabiliser , I tend to use pieces from old cotton/linen shirts, it's rather nice to think that there is a hidden piece of fabric inside every kilt.
Whereabouts in the UK are you?