I use both PCBWAY and JLCPCB. If I need it 'guaranteed' for a time, then PCBWAY is my preferred option (I love their transparent ordering and tracking system), JLC is a bit hit/miss with timing, but as others have said, the quality might be a little better than JLC, but the stress is higher.
Sadly I've stopped recommending UK manufacturers for most customers jobs, the lead-time's aren't any better for 'standard' prototypes - quality really isn't any different. And the prices are x10 more.
I remember a time when there was over 500 PCB companies in the UK, now it can't be more than 50 - those few remaining PCB companies in the UK seem to surviving and 'happy with their lot' - however, the ones I've spoken to recently don't seem to be investing in their facilities or systems. I'd happily pay a 'sensible' premium for UK made PCB's if they had the online tracking visibility, online front-end and turnaround of PCBWAY.
And yes, the legislation on processing your effluent is different in China and the EU, but that doesn't explain the 10x difference. Rant over.
EDIT: english..