I have installed the braided lines when changing nothing else; they did make a difference. Not a huge difference, but enough to notice if you are looking for it.
But one of the downsides of them is that the outer SS braid gives you no clue as to when the inner PTFE hose is starting to fail. The outer visible braid is only to provide abrasion protection, it has nothing to do with holding pressure.
I have them on all my Triumphs, in fact I moved them from the wrecked TR3A to the replacement TR3.
Not listed on the web site, but I'm pretty sure Ted Schumacher can have them made to suit your Herald:
https://www.tsimportedautomotive.com/
I felt the ones I got from Ted were better made than the ones from Rimmers; they had ends that matched my car instead of the adapters that Rimmers uses. But the ones from Rimmers seem to work fine.