Thanks to medecine hat and Confab but pressing the cartridge button for 5 seconds or more merely activates the cleaning routine and the catridge, which still contains ink, stops in an inaccessible position on the right of the carriage. Pressing the button does not work until the catridge is empty.
RTFM click here From the manual (page 33):- Lower the output tray at the front of the printer, the open the printer cover. Hold down the cleaning button for 3 seconds until the print head moves left slightly to the cartridge replacement position and the power light begins to flash.
Further to the above look at page 41 of the manual click here which states "To replace an ink cartridge before it's empty see "Replacing an old or damaged ink cartridge" in the online reference guide." The online guide is found on the installation cd for the printer click here then look at "opening the online guides" The file you want is ESO750.exe found in the online folder of your installation cd. good luck
As above, switch printer off, restart printer and when the carriage starts to move switch off at mains, this will allow you to move the carriage by hand. Remove cartridge but do not put new one in yet, close cartridge lid and restart printer, it will register that there is no ink cartridge and you can then install a cartridge as you would when it is empty. This method resets the ink counter to zero, it then knows it is starting with a new cartridge. Good luck, any further problems get back on.
Sometimes I feel quite stupid through not doing the obvious. Thank you Smiler for reminding me that somewhere in the depths of my accumulated junk I have an online guide where it quite clearly states that pressing the paper feed button for 3 secs moves the carriage to the centre of its run. Q.E.D. Thanks also to LAP, huggyg71 and SantasLittleHelper for the alternative !