I have half dozen Seagull kits and they've all been excellent
Build quality have been better than some top end kits. Supplied hardware more than adaquate for each plane
The only hardware I've changed is the spinner, which is all plastic and not recommended for 4 strokes
I also find the instructions as good if not better than H9, rather surprised some people find them thin on paper

I've had two Hanger9 kits, not really happy with either
The build quality and finish looked very patchy, worse than My first build
Had to upgrade the hardware on both of them, pushrods, horns very cheap and flexible
And very over priced compared to the Seagull kits

I haven't seen the Sparrowhark kits yet, so can't comment on them individually
I have the Seagull Extra 260 (160) and the Decathlon (40) waiting to be built, both kits look excellent