I usually use 10mm rope, but wanted 15mm for a parlour trick, and could not find 15mm thick rope in the magic shops. I found this on e-bay:
http://cgi.ebay.co.uk/Soft-extra-thick-w......0%3A1318
It is soft cotton, and hollow, so ideal for gaffing. Be warned though, I think the main sales demographic is the bondage market!

yes it is the bondage market also called Japanese soft rope. There are a few distributors. I left the links on another thread on rope.
better deals: http://cgi.ebay.co.uk/JAPANESE-SOFT-BOND......0%3A1318

Or go to baroniantrading.com for larger quantities.

The really cool thing is that it comes in black!!

Black and colors

Click here to view attached image.

Thanks for the info Ian. Do you know if it is 10mm or 15 mm?

PS I'm still practicing the 'Dances' routine!

Here's an ad that states 10mm.
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?V......09940710

Is there a reason you prefer 10mm?

Wow I must admit we don't even think about rope in MM here in the the colonies.

Has to do with the fingers covering the rope at integral times in the routine. If you take two widths of the 10mm rope, it is the width of your thumb, two widths of the 15mm side by side, excede the thumb. I play on the optics of the rope above and below my fingers and its just a matter of simulation and continuity. In general, there are rope pickups and c&r's that work well with any rope, but in my case size matters. LOL.

I always use 10mm, but wanted to try out 15mm hollow core for a parlour routine where the rope will be heavily gaffed (gimmick + other 'storage' possibilities).

I sell some rope that is 15mm. If you haven't found any by now, let me know.

Thanks to both Frank and Ian for the information /advice. The e-bay link I posted initially was for 15mm, which I have now got, and is what I needed. I just couldn't track any down in the UK, which is why I put the link up there.