Yes, Worldbridge doesn't even offer any priority services for UK visas anymore.
The only place you can purchase the priority service is here through the VFS Global website) ($510 for settlement (fiance/spousal) visas or $170 for all other visas):
http://www.vfsglobal.co.uk/usa/user_pay_services.htmlThe service is still the same (UKVI offer the service in Sheffield - they move your application to the front of the line for processing), you are just purchasing it through a different website now.
And there is no fixed amount of time in which it will be processed. When Worldbridge did it, UKVI offered a 15-working day service, but then they realised they couldn't guarantee they could get the applications processed in that time, so they changed it to
'This service allows settlement visa applicants to pay to have their visa application placed at the front of the queue once received by the UK Visas and Immigration Decision Making Centre (DMC) in Sheffield, to commence processing ahead of other visa applications.'A few months ago, priority applications were processed in a few days, but right now, it's been taking up to a month (maybe longer if they need to request extra documents), and 2-3 months if you didn't purchase the service.