Martin, do you have the original?
measure the length of the tube from below the flange.
Then try here, https://www.merlinmotorsport.co.uk/s/instruments-gauges/vdo/vdo-dip-tube-senders/manufacturer:VDO
Hi Paul, it is 195mm from flange bottom to tube end which seems midway between the standards on yr excellent vdo link.I will call their technical line tomorrow to see what is best. Many thanks Martin