From what I've seen of The Dogs' Trust, their staff are tremendous at understanding their dogs and making sure they get placed in an appropriate family. So if you have a DT near you, I'd be inclined to go there, with Storm, and let them guide you.
Otherwise, I hear good things about Border Collie Rescue.
Hopefully one or other of those will be able to find you a collie or collie x that's not interested in sheep, and is a good choice for an active family pet who will get lots of stimulation, mental as well as physical
Oh, and is ok with cats
And not too clingy.
I suspect that any of the above would have you introduce Storm to your potential new family member at their premises, on neutral ground, so they can become playmates before the new dog arrives in Storm's territory.