Hi cheezz, I just went into Photobucket and deleted a bunch of my old albums.
When you get all those Pay Up messages, just click on the X in the upper corner and it will eventually bring you to the albums. It will look hazed out for several seconds....give it time and they will refresh to the actual photos. There is one LARGE top level one and twenty or so individually named albums. I cleared out all but three of my albums and deleted or moved photos in the top level batch to those. I know I reduced the total size, but not sure by how much. I still get the Pay Up message.
When you get to the albums, you can either delete the whole album (select it, then look over on the right side of the screen. There will be a DELETE ALBUM option. You can also delete individual photos by selecting the CHECK on the photo and DELETE at the bottom of the page (in the blue menu bar)