It seems OK for what it is.
For sole trader, I think FSB membership is £120 a year (more for 1st year). As you say, you get tax investigation assistance with that if ever needed so the fee is worth it for that alone. By the time you claim tax and class 4 NI relief on the FSB fee, the real cost is more like £80
The Co-op account is cheaper than free as you get a £25 annual bonus.
So basically, you get a business banking account for £55 a year with tax investigation insurance thrown in - plus any of the other things on offer if you want to use them.
The only small down side is the odd telemarketer trying to sell you something while trying to make it appear that they are representing the FSB.