We could have called out Bonner of Ireland (Aran), Jamiesons (fair isle) or even Inis Meain (aran-ish)... Or tons of other companies.
I don't mean to piss on your parade or anything, Howlin by Morrison might be good, but there are so many good knitwear companies around, but very few similar to Inverallan. What sets Inverallan apart from the rest is the fact that everything is custom made by hand. But no particular type of knitwear og style is synonymous with Inverallan. They made aran, fair isle, som crazy argyle knits and of course what ever the customer wanted.
Most Howlin by Morrison knits appear to be machine knit. So sorry if I didn't see the imediate connection. Though Howlin looks rather good. No question about that.
Actually, I remember a couple of makers of custom fair isle knits. I'll try to find the links. They would probably be able to do some aran knits too.