This might help www.gardeningblog.net/how-to-grow/butternut-squash/
I love butternut squashes but don't have any space for them - good luck.

They are not really suitable for growing anywhere except very warm parts of the country. there are far easier and better tasting Squash out there. We grow Crown Prince, Ukuchi Kuri and another one whose name I cannot recall. They all do far better. Look out for the seed of ones which have the shortest growing season.

I think squashes need to be pollinated by other plants and can also to be cross pollinated by nearby plants of the same family, i.e., cucumber, gourd, etc. Is it possible that this could this be your problem?

They are suitable for growing in most of England, perhaps not all of Scotland. Looking at our allotment site which is 1000ft. above sea level in Birmingham there is a bounty of butternut squash on some plots.
That seems to be the answer: plenty of compatible pollinating squash plants.

I grew them in a cold greenhouse, three plants, one on each, they had to be left a long while to ripen, virtually until the stem went dry, before that there was little taste and a 'soapy feel' if that makes sense!
Won't do it again they took up so much space......

Well they might grow above Birmingham, but here we have to grow all our Squash in the polytunnel. We tried them outside and they all succumbed to the cold long before any fruit even appeared, never mind ripened.

I've grown some fantastic plants this year, 12ft or more of luxuriant foliage and flowers all along! But, just two squashes, about 2 inches long at the moment, and I knocked one of them off this morning when I walked past it!