Thanks for that Rob1234.
For info, both part numbers are recognised by Philips and refer to the same drive belt which is still classed as obsolete.
However, further discussion with Barry White from Philips revealed that the printer drive belt is contained in a "small parts kit" which also includes a paper guide, eject spring, eject key adapter, left & right guide holder. Part number for this kit is M1350-64550 and costs £64.07.
Cheers for that Barry, and in the words of your 1976 hit: "Let the Music Play"!!