My first port of call for a recommendation is always the sales section in this forum. It’s even easier now as sales listings have the country prefix so you can see at a glance which are UK based.
Otherwise I’d suggest eBay (and the recommended eBay thread here). Be aware that the best buys on eBay often require a base level of knowledge to avoid buying a dog.
To buy from a dealer you’re always paying their profit so you’re not really going to get good deals. If you’re happy paying a premium you’re probably stuck with the UK dealers you’re already aware of.