They were my broker for years. One day they sent me a letter demanding 700 that they claimed I owed them from some 2 years before. It turned out they had sold some of my shares twice (their mistake), and neither them or I noticed this at the time.
Also they refused to give me a record of all trades/losses over the last 5 years when I left them.
In the interest of balance, their actual dealing service was generally pretty good, and they have made efforts with the website in terms of information, research facilities etc, although all these can generally be found elsewhere.