ebay is your best bet - i'm selling all mine on there and going for silly money.
a pair of my dumbells went for £220 2-3 days ago.
i think i paid around £500 for my full set which now has a street value of around £4K-£5K
Managed to get something together between Bulldoggear, Rogue and eBay... They've all been pretty good with deliveries.
Word of warning for anyone using fitness superstore. Their stock isnt updated correctly on their website. If you look on their social media or Trust Pilot they have a lot of complaints. Understandably they must be busy but should do what a lot of companies are doing and simply disable new orders. A lot of their recent 5* reviews are from people supposedly going in to their store even though their stores are closed.