In response both to Vestris’s Sep 18 post, and to more recent developments on the subject of Tie Patterns:
Top quality, pre-cut interlinings for neck ties are available on line. They come in various materials, weights and sizes, and work out at roughly £1 per tie at point of purchase.
They’re made in The Netherlands by AC Ter Kuile, and sold through Etsy from The Thackery, which is based in the US. As I live in the UK the postage is around £10 and I expect our beloved Customs people will charge something too, bless them! I’ve ordered a total of 15 (they sell them in batches of 5 per weight/size) so I imagine this will increase the unit cost to nearer £2.50, not to mention adding about 4000 ‘fabric miles’ to the process!! 
Wondering whether I could buy direct from the maker, avoiding these additional costs and carbon, I learned from their web site that they have a web shop selling their fabrics directly per metre, with no obvious minimum quantities. Interestingly, they also provide a cutting service for their tie shapes. I imagine there will be a minimum order requirement for these to make it cost-effective. I can’t contact them to check as it’s still Easter holidays.
Is there enough interest in making ties to warrant getting together to place a joint order that makes more financial - and environmental - sense? I’ll happily act as point of contact - at least for the UK (I would unflinchingly offer EU too but with things going the way they appear, this might not be wise!) so please let me know by initially replying to this post if you’d be interested in taking part.