Many thanks oldturkey03 however I think your method may be generic for Canon printers, as on the IP2600, the pads are inaccessible without dismantling the casing. I did manage to pick them out with tweezers and clean them but could by no way fit them back into the small rubber frames. Removing the frames and fitting them outside the case was no help as I then couldn’t then refit the frames. However after around 3 hours of persistence in trying to dismantle the case without breaking it, I finally did it.
My method was as follows:-
1) Switch off the printer at the point where the cartridges are to the left side away from the ink absorber. Unplug it and remove the feed cable.
2) Remove the side panels (which wrap round at the rear) by sliding towards the back. This may take some effort but they will eventually release.
3) With the front flap dropped and the lid raised, unscrew the two small screws at the front on the extreme left and right.
4) Press a flat head screwdriver or similar into each of the three arrowed slots at the rear. Now lift the case off the base.
5) The black and white, and colour ink absorber pads each sit in small rubber frames, which themselves are slotted into a white sliding undercarriage. If you clean the pads regularly, the white undercarriage may not be splattered with ink as mine was. But if it is, it can be removed by releasing the four lugs, two on each side, by a bit of wriggling. Then also release the two rubber hoses from underneath, noting the route they take to reach the undercarriage.
6) Clean the undercarriage, rubber frames and pads in warm soapy water and dry.
7) Replace in reverse order of above.