Depends what you're looking for too. I snagged some pro-style dumbbells from Fitness Superstore just stumbling over them by chance. I wouldn't have been checking their site usually as I'm after some specific things that they don't (seem to) carry.Where are people getting equipment these days?
Strength shop is slowly starting to get stock back but not entirely sure of other sites worth checking...
They don't have back in stock notifications but knowing they had more due I kept checking and grabbed another couple of light pairs last week.
I'm only really looking for iron plates now so options are limited as very few UK stores carry old school style iron.
Origin - best price for rubber hex dumbbells but stock comes in randomly. I had good luck emailing and they had stock in the warehouse not shown on the site.
Mirafit - good experiences with all my orders from them. Seem to be getting restocks relatively frequently
May be worth giving Fitness Equipment Northern Ireland a call to see if they have ETAs on stock. At the start of lockdown they were still receiving shipments of plates and bars and shipping to rUK isn't too bad if orders are split to under 50kg.