From the Electoral Commission website instructions on obtaining a Voter Authority Certificate:It still costs to get a confirmation certificate unless you know any photo booths to get a passport photo which don't charge.
Nobody should have to pay anything in order to register their vote.
The bus pass includes a photo - when you go to the council office to apply for one they take the photo there and then to put it on the card. No charge. Presumably they can do this for the VAC too.You will need to submit a photo with your application. The requirements for the photo are similar to the requirements for a passport photo.
If you need help taking a photo, then your local council will be able to do this for you.