I have - great investment - became an associate director in a bank at 28 then senior manager by 30 largely because of it. Massively rocketed my career. More than just the amazing cv, good agencies will QUANTIFY your value and make you realise you are worth so much more than what your manager/past companies have led you to believe.
Citycv is the one I use and recommend my friends. Owner of company worked in HR for Goldman sachs - most over subscribed investment bank in the world. And she was the one who did recruitment there.
CV she made for me was phenomenal and I am not getting paid for this just saying what she did for me. This was years ago mind, no idea if the quality of her work is as good as she may be far more removed from it now as was fair while back.