Dont worry.......
First of all, it wont be registered on your credit file as it is not a credit agreement you have/had with the power company, however if it went to county court for a judgement (CCJ) then it will be registered on your credit file. It is unlikely that it will get that far though due to the low amount outstanding.
You should first of all contact the power company and dispute that fact that you have had no bill or subsequent reminders. this will usually delay any potential court action (if it ever gets that far) as you are disputing the "debt". Therefore if a judge were to look at the case, it would normally be referred back to the company for further investigation.
The simplest course of action (seeing as you dont seem to dispute the fact that you actually owe the money) would be to offer them say �10 per month until it is paid off. If you dont have any money...then they cant expect you to pay it off in one go. If you do enter into a repayment agreement with them try and make sure you stick to it though!!!
As for the bayliffs, I canot see them sending the baylifs round to collect such a small debt.....just call them and offer �5 or �10 per month..and they should accept.
Good luck...but dont worry....