Well it certainly sounds like you have found the problem.
Could the rubber pipe/connector have gone porous?
If you don't want to pay someone to fit a new one for you, then you may just need to live with it for a while longer.
As you say it only happens when refilling, and you don't fill up that often so not a major problem really.
I have a similar, but different, issue with my bike in that if I fill up 100% I get a weep of petrol from the seal around the top plate on the tank.
Now I only ever put 10 litres in at the 100 mile point on the trip and it's happy days.
Edit - Have a look at this ebay listing from Caffyns - they say it's a common cause of fuel leaks
https://www.ebay.co.uk/itm/GENUINE-V...-/321721222265
Cheers
Dave