Not been, but Bubbles is very well known in the city as it's probably the least discreet location you could pick. The local paper has written about the place a few times and sent undercover reporters on more than one occasion. It faces straight out to the train station entrance and the rather busy bus stop and taxi rank. I don't know if it still happens, but when I used to take the train to Derby, Bubbles clients often used to get jeers and whistles while they waited to be let in.
The website and list of girls definitely looks to have improved. If you're local to the area, it's risky standing in such an exposed place waiting to be let in. If not, fuck it - who cares?