I am conducting a research about online brokerage in UK market. I notice from some information source that very few British people trade stocks online, does anyone know the reasons? Could you please provide me with some data (or link) about number of individual online stock trading accounts in UK, quantity of transaction done online, etc? Thanks in advance.

The reason is that they prefer trading derivatives for taxation purposes. Have a look at the popularity of Spread betting and Contracts For Difference (CFD)
WHO KNOWS????????