By coincidence I just contacted Bainbridge about Globe impellers - their Nick Robinson replied:
"The impellor for the Yanmar 1GM is Globe model 321, you can order this from any UK chandler using the Bainbridge Marine part number Q133009. RRP £13.60."
Worth remembering in view of the large number of people who seem to have had trouble with the oem Yanmar part. Apparently, they're rated to run dry for 15 minutes.