If I may add a couple notes about the Ditto Story use of gargoyles...
The other North American clans I've mentioned (like Grand Tetons or North Cascades) are ones I've created in my own writing (as opposed to those on the original show). So while it hasn't been 'officially' established that the London Clan has connections with them, it's certainly reasonable. However, due to the difficulties in getting across the pond (gargoyles can't just buy a ticket and catch the next transatlantic flight

But it's safe to say the London Clan would know of their Tetons counterparts if you want to write that.
Also note that Erik and Abby really aren't typical of their kind. Most gargoyles tend to be rather reclusive since they're so vulnerable in stone sleep. But their experiences in the Ditto World have allowed them to open up and be a lot more sociable. The London gargoyles would probably be receptive to meeting Varna (meeting an elf would no doubt fascinate them); they just might not be quite as open about it as Erik and Abby would be.
(If this is confusing, please ask questions here or by PM). [/ramble]