Hi Darren, funnily enough I was thinking of you and wondering how you are!
Butternuts are a pain in many ways, unless they have a whole season of full sun and warmth. Perhaps yours did, whatever, they are not ripe and the only thing is to wait until frost kills their leaves, as they do carry on maturing when other squashes give up. Then as soon as (or just before) frost kills leaves, bring them indoors to warmth and some curing/sweetening then continues for a few weeks, as long as skins are hard in the first place i.e. not like marrows!
Frost-wise we escaped any just now and the weather is about to tun milder, so it may not freeze until November. So perhaps by Christmas yours will be eating some decent Butternut!