I ordered some horsehair canvas, body canvas and collar canvas from a place called Textielstad. The shop is miles away, so it was an online purchase. It's worth me checking it out because buying from Kenton or Bernstein & Banleys takes longer and the postage cost is higher. I also bought from a German supplier, but it turned out to be different from the advertised product and they were unhelpful via email.
Anyway the cloths arrive on Tuesday or Wednesday, so I can asses them. It may be a good source for people in NL, Belgium etc. The cost is quite low too with the haircloth at just €6.50 rather the £9-10 I would pay at Kenton plus a sizeable postage fee.
Do you know http://www.beautyvof.com/. They're quite good as well.
Thanks, I've bookmarked the site. I'll have a look through their catalogue.
The cloths had arrived when I got back. The body canvas is actually pretty good. Firm, flexible, but light. The collar canvas is a bit thin. Either that or I have just been using thicker stuff. I had a roll of collar canvas that was more like that I've found in vintage garments; a bit more of a slight honeycomb texture. We'll see how that goes.
If you're looking for interfacings, you could have a look at A.C. ter Kuile (https://actk.nl). They have around a 100 types of interfacings, which, correct me if I'm wrong, they produce themselves. They sell different kinds of fusibles, horsehair, haircloth (around €5 p/m), etc.
For spare parts and accessories for industrial sewing machines and pressing equipment, you could try Andrevo (http://www.andrevo.nl). They have an online shop as well, but that's just a fraction of what they have. So, if possible, I would stop by their store, which is located in Amsterdam.