I'd never tried yoga before, but when my colleagues started nipping to the newly discovered bikram yoga classes nearby and returned with rave reviews my ears pricked up. I say 'nipping', the classes actually last for an hour and a half but in the heat, you can't just whizz through these moves.
More popular than I imagined, every class I went to for three months was jampacked and full of people of all ages / ability / sizes / sex, so as a beginner, I didn't feel uncomfortable. This was also partly down to owner-cum-instructor - Libby who was a fantastic teacher. She explained every move, why it was good for you and what it was doing on the inside and the outside. Plus, if you started to feel a tad too overheated (these rooms really are hot), she was there by your side, making sure you had enough water or suggesting you sit out of a few poses - which by the way, is no sign of your ability, the heat simply effects you differently on different days.
Since moving away from Leicester, I haven't been to Bikram yoga since and would like to try out other variations before returning to Bikram, but if you're looking to try it out, I couldn't recommend Libby and her team highly enough.