If I change my name without deedpoll can I pay my bills in the new name?

Hi I want to change my name , just drop my last name and start using my mums surname instead, my question is I want to do this without paying for the deedpoll, I have read on CAB that you can use another name anytime without having to obtain any doents as long as you can be shown to be known by others in the new name, but when I come to set up my bills can I use my new name to do this?? without it being illegal or having to show any proof. Any info would be great Thanks :) (I live in the UK)