I had a bad experience with Trafalgar nursery back in 2005/2006, and eventually moved my child away from there to another local nursery that I was much happier with. I know lots of other mums whose children have gone there, some of whom also moved their children, and others who stuck it out but were not 100% happy with it.
One problem (of several) that I found was that they had a high turnover of staff, and, as they were a chain, they also used to move staff between nurseries quite frequently to balance their ratios. For example, if their nursery in Richmond had too few senior staff because somebody was off sick, my child's key worker might be drafted in to make up their numbers, which disrupted things for us. (That happens to a certain extent within all nurseries, but in my experience the effect was greater in this commercially run chain of nurseries as it seemed to operate with minimalist staff-children ratios). Also, when my child was there, they would do things like allow the nursery to be used for filming training videos, photography for childcare books, or to provide training for several college students at a time. The effect was that they had a significant number of strangers passing through, with apparently little regard to how that might affect the children. Other problems at the time were poor food, indiscretion in dealing with complaints, a general coarseness and/or coldness in manner of a small minority of staff, and a defensive management style which discouraged people from raising issues. I also noticed that their Ofsted report used several of the same phrases that the manager used in her sales pitch to prospective parents, and praised the nursery for having policies that I knew were not always followed by the staff, so I have never since particularly trusted Ofsted reports as a true reflection of a nursery's performance.
The nursery has had a couple of high profile issues, including this one from which I believe they were cleared of any blame (but those of us who were there at the time will never forget the horror of it), and a scandal involving a particular member of staff in 2010 which I won't link to because the nursery itself wasn't named in the news coverage (though they were obviously responsible for his recruitment, training and management).
The nursery has a different manager and staff now to when I was using it, so I can't comment on its current status. All I would say is, go and visit as many nurseries as possible. Look beyond the decor and the policies, and judge them by the warmth, love and respect with which all staff treat the children, including the shy children who don't naturally gravitate towards them, and the mischevious children who require more patience and skill to care for. A good nursery worker should have an obvious aptitude for the job, as no amount of training can compensate for a basic inability to relate to children with warmth, affection and intelligence.