Did you find an answer?
The answer is that there is no particular delay because they don't guarantee the priority service will only take a specified number of days. It really just depends on when you applied and how busy they are.
Current processing times, based on people's experiences here on UK-Y:
- 3-4 weeks with priority processing (possibly longer if they request extra documents)
- 2-3 months without priority processing
If people are getting their applications in less than 3 weeks, it's because they are managing to speed up the applications a bit more now (back in January it was 24-48 hours for priority, which over the following 6 months then increased to 1 week, then 2 weeks, then 3 weeks, then a month... now it's speeding up again and people are getting them faster - in some cases, just a few business days).