Thanks Peter P. Oh how I wish I lived in London, but unfortunately that is limited to days off.
Doing a bit more research (in mostly East England) I found that hours are sometimes listed elsewhere in the profile, such as the availability tab or interview tab. Of 31 profiles analyzed, a little under half listed their working hours, with the average start time for WGs at 10:30 am and the average end time at 10:30 pm. So for very late night punters this means slim pickings. I have been too busy lately so I will have to work less and/or free up some time during the day or mid-evening. I will also add a working hours query to my generic text.
Also, 4:30 pm should be the mean working time, which interestingly seems to coincide with what I found to be punters' rush hour in Soho. So that should be when the most girls are working, yet also when the most punters are active thus nullifying their availability.
Profiles: 31
No hours listed: 17
Hours listed: 14
9am till 9pm
10 a.m.till 12 p.m.
9am - 7pm
Morning, Midday, Night
10 to midnight
10am to 10pm
After 7pm
10am to midnight
10am to late
10 AM -8PM
11 am - 2 am
11am till late
9am - late
11am until midnight