Evans do carry a few bikepacking style bags but there’s no guarantee that any given shop will have what you want/need.
It’s one of those things that’s hard to make recommendations because every frame is different and we each have different demands of what we want the kit to do. When we started bikepacking (though we’d done similar before and just called it overnighting/bothying) there was only really Alpkit, Wildcat and I think Apidura available. You could get Revelate if you ordered it directly from the States. After lots of prevarication I went with Wildcat so now have a slight bias towards them.
Remember to only pack what you need, not what you want. There’s a big difference! Colin will also say that it’s better to invest in light and compact kit which is true but that’s further down the line. Of course using that good quality kit isn’t restricted to bikepacking – the per night cost of my quilt is now just over £1, a mixture of bikepacking, camping and sleepovers.
Last point: don’t panic when you see ultra light kit lists as that’s usually for UK summer. Once you get to this time of year things just get heavier and bulkier (though not by much).