The obvious (and cheapest!) option would be to get hold of the Sheps yeast, either scavenged from a cask or I'm fairly sure that 1698 is bottle conditioned with the production yeast - I've not tried it myself, but it's widely available in supermarkets.
Yes Verdant is a derivative of 1318 London Ale III, and is generally the least bad dry yeast for British styles these days, although some people find the vanilla note a bit off-putting. Liberty Bell is a decent alternative, and might be better suited here.
But I'm not sure you really want a 1318 for this kind of beer, it's maybe got a bit more character than you want in something like WPA. A really under-rated yeast for this kind of session beer is WLP041 Pacific Ale which despite the name is a British yeast, probably a derivative of Gale's. It gives a really easy-drinking character which works well for something like this. I see GEB don't have it, but they do have what's meant to be the Wyeast equivalent, 1332, which I've not tried.
As an aside I'd regard WLP002 and 1968 as distress purchases these days - there's plenty of better British yeasts out there, and wherever they came from originally, they certainly don't have the marmalade character that is so typical of the real Fuller's yeast. Which is easily harvested from cask, 1845 or Lancer, or Imperial A09 Pub is a much closer match.
