Timely, I just bought a new roll for myself last week.
I, too, use the medical exam table paper that I brought with me from the U.S. When I ran out, I looked for an equivalent in the U.K. and I thought the "couch roll" was the same thing so I bought it. Well, I should have noticed that the description says "2 ply". It was basically a giant roll of toilet paper!
So after some intensive search on Amazon and Ebay, I ended up ordering the medical exam table paper from American Amazon.
This one.Even with the shipping, it was much cheaper than any other tracing paper.
It's not as wide as the "real" tracing paper but it fits well on my kitchen counter where I trace my patterns and it's 68m so lasts quite a long time. I can also use the scrap paper as a stabilizer.