I was just looking at the pricing model for Alpha:
I think I would be more inclined to subscribe to that plan if it offered a small number of premium trades each month for free or a number of free premium trades under a specified value.
Thinking about someone who wants to start investing in shares but with only a small amount of capital. Any small gains are going to be offset by the 50p fee which will not help.
I can definitely see the potential of this plan when investing with a lot capital though.