I've done yeast offs between Pub, WLP02 and 1469. Pub has always been the blind taste test winner at the homebrew shop. If fact, have done same with 4-5 yeasts and Imperial has always been #1, and not sure why.
All the purported Fullers yeast strains floc like crazy. Big old chunks. A bit of Lyle's golden syrup seems to help. Not only available on Amazon, but also in my local Kroger affiliated supermarkets and World Imports. Or you can make your own invert. So, you may need to rouse the yeast, especially if bottle conditioning.
I've recultured Fullers yeast successfully from one of the bottles that
@Northern_Brewer kindly brought to seattle. Made a second partigyle with it and some darker grains, so didn't taste the marmalade. And for some reason, after close to 10 years of being available in the US as bargain prices, First Gold seems to have gone off market. But Fullers + First Gold should be a nice pairing for a bit of marmalade.