If you are using a PC in Commercial Road Library and want to manipulate images, use the PaintNet software installed on all machines. This is an excellent substitute for Photoshop. PaintNet features sophisticated image re-sizing. You can adjust levels and colour balance and, most importantly, use layers.There is a wide range of tools including curves, clone stamp and magic wand. It is free to download, so you can use it at home too!
All of the Macs in the Library have Photoshop, for those projects where nothing else will do!