I'm not sure what you mean by a finance agency. If you are referring to one of the outfits that charges a fee for doing this then the answer is a big NO - don't waste your money in this way. If your finances are bad enough for you to go bankrupt you don't (or shouldn't) have money to throw away in this fashion.
You can get the forms from your local County Court or download them from the internet. If you are confident you know what to do to complete them accurately then do it yourself, but there are aspects of the form filling that you may not be aware of which a money adviser could help with. Otherwise, use a free advice service such as your local CAB or by calling CCCS.