How hard is it to find denatured alcohol?

In the US I found it to be very easy. The problem was one of quantity, since although it was widely sold in hardware stores it was very tough to find in relatively small amounts. I think that a half-gallon can was the best I could manage in Maine.

In the UK you'd be looking for "Meths" or Methylated Spirits, which despite being purple is essentially the same stuff (it has additives in it designed to discourage drinking). Widely available at chemists (drugstores) and hiking shops in hiker-friendly sizes.

For Europe you should ask for "alcool a bruler" instead; and again, it's essentially the same stuff and is widely available. Meths stoves have been very popular in the UK, Europe and Scandinavia for a long time, so fuel availability is generally excellent. I'm afraid that I've no idea on the situation in other countries.

Any auto parts store in the us should have Heet in the yellow bottle. It works fine in alcohol stoves. it comes in a 12 oz bottle

Every gas station seems to have the yellow 12oz bottles of HEET here in Minnesota. I wonder if it's that easy to find in warmer states.