No it is not same way as ASL and BSL and if it is same way and how come i can not able to understand ASL
I used to be BSL tutor for 11 years and yes no need to use
voice because it does help the students to learn by use their eyes instead of ears, because we deaf people only use their eyes to watch the sign langauge, And the students asked me does i use my voice I replied yes I does and while during on the course am not allow to use the voice and it very important because deaf people can not hear when hearing people speak like eg: when hearing person say 50 and deaf person not sure they mean it is 15 or 50 because it look similar so it very important for student to understand that it does look similar like 15/50. 14/40. So you try then you will understand what i does mean.
To be honest there are nothing much similar between ASL and BSL.
Yet I do use my voice with signs only for some reason lol when am angry or piss off