Was gonna suggest a brillo pad but maybe better sticking with the lens cloth![]()
sandpaper... *cough* oh!... I mean a glasses cloth![]()
Lens cloth and/or lens tissues and cleaning-fluid, which should be in your camera bag, along with a blower-brush for the optics and a small paintbrush and an old toothbrush for the camera exterior...lol
Next trip to Jessops, what are you going to buy?![]()

the three key tools in camera care are;
1) lens cloth - sorts out most average cleaning issues.
2) lenspen - perfect for removing smudges and finger marks from lenses.
3) rocket blower - can blow dust thats stuck in awkward nooks and cranny's and can also clean camera sensors, though the rocket blower has a few haters because of how big it is.
for the Lenspen kit