I'd like to point out that I have only commented on my personal experience. My own circumstances are/were that I have bad credit and needed a bank account that wan't a basic account. For me, paying a fee for someone to point me in the right direction was well worth it. Some people will differ in their opinion. It worked for me, I dare say some will be less lucky.
I suppose at the end of the day, no one can absolutely guarantee acceptance for banking etc, but I don't think that is what they're doing. They are just saying that you'll get your money back if you don't. I took a punt, it worked and I'm happy.
A friend of mine also applied (see my previous posts). He had an IVA and also got an account. Again, I'd like to point out that these are personal experiences.
From what I can find out (I know people), this seems to be a reputable company with other businesses other than the lesstha.... one: recruitment and property is the information I have. Only companies dealing with mortgages are FSA regulated, this one isn't and doesn't need to be. That's not strange at all.