In reply to d1griffiths:
The Trangia fuel bottles are HDPE (high density polyethylene, aka 'fancy polythene'). Paraffin is often supplied in an HDPE bottle, e.g.
http://www.diy.com/nav/garden/garden-buildings/greenhouses/greenhouse_acces...
My only concern is that paraffin does tend to get everywhere. I was going to use the term 'creep', but that seems to have a specific meaning with paraffin at low temperatures. I mean that the oil tends to spread out if drips or runs occur at the spout. Meths, on the other hand, simply evaporates cleanly.
The design of the Trangia bottle closure is also unusual, in that the bottle has an internal thread, which is reinforced by an external, aluminium collar. It uses a silicone O-ring to form the seal.
Most simple bottles have an external thread, and a good cap has an internal thread to mate with this, but also should have a deep, internal, angled neck that mates with the smooth bottle opening inner face, forming a good seal.
I don't see a problem with using a Trangia fuel bottle to carry paraffin.