Butternut Squash - are they the same as courgettes

I'm not sure lack of pollination causes tip rot.  I think it's dampness.  If you remove the flower when it begins to shrivel it could help.

It seems to happen with the earlier fruits here, and we had the same problem Thestens.

It may be that its just too damp, and the conditions are poor for them to get going properly.

Paul and Aunt S. have got good ideas here, and they could be the solution, as I keep peering at our forming ones, and wondering if they'll thrive! If the stems are forging ahead, you should get a few more fruits forming, and they could be fine! Depends on what sort of weather we get over the next few weeks...