The most important thing about these toilets is that they appear to be the last of the few station toilets for which you don't have to part with 30 pence to spend a penny...
They've always been clean when I've been in them - wouldn't say the lighting is particularly inviting though, and they have those really irritating taps which you have to press with one hand whilst washing the other. In my experience the hand driers always work and there's almost always paper in all of the toilets.
One of the best things about these toilets is the amount of conversation you get to overhear from all sorts of people. (Wouldn't be surprised if Sherlock Holmes solved some of his cases with information heard here. Although that would mean he was hiding out in the ladies.) Last time there was a lady crying in one of the cubicles and then having a massive row with someone on her mobile in a foreign language. (Not a nice thing to hear but interesting all the same...) It's also a favourite spot for people touching up their makeup and sorting their hair before continuing on their journey as it has large mirrors.
Some people may find it a little dingy, but I like them. They're free!! 
