Sensor is still working 3 or 4 days into its immersion in fuel test. So im happy that it will be going into my working tank.
I bought an extra relay and 12v-5v converters so I have made up another module, which is available at cost of parts (£15 plus postage) if anyone wanted to have a go themselves. Or I can buy in another sensor and make a whole one up at cost for £40 to a provided OEM sender unit. That would be plug and play.