Sorry to reply to myself but looking around, the cheapest pipe seems
to be the Flopast PEX in Screwfix, part 54479 and 38914. I would have
preferred PB rather than PEX as I had read here that Pb was more
flexible. Are these prices good, and can I find better anywhere else?

Has anyone used Flopast pipe; is it any good?

Also, I understand you need a special pipe cutter to cut Pb and PX
pipe. Can anyone show me a suitable (and cheap) one in Screwfix, so
that I know what I am looking for?

Thanks.