I found some at a supplier of high tech lubricants (here in Australia). I don't know what they do with it, but you might be able to find some locally if you do a web search. Here it was $20Australian (= about 8 pounds UK) for 5Litres, which will last me for quite a while. It came with a certificate stating that it was 99% pure. I had to supply my own container.
TEA is widely used commercially and also by hobbyists and homebrewers of cosmetics. Perhaps you can find a local supplier in that category. I'm sure you know it is triethanolamine, but it didn't hurt me to say so.
It also wouldn't have hurt me to tell you about the Dow Chemical website with a brochure for downloading in PDF format that tells all the possible uses of MEA, DEA and TEA from which you can get some ideas about where to look for users, as well as all the technical information you could possibly want about things in which you have no interest. www.dow.com.
I note they also supply Propylene Glycol (listed as: MPG, PG, MonoPropylene Glycol, 1,2-propanediol - 99+%) - which also seems difficult to source in the UK: at least, without a trade account with a chemical supply company.
Useful resource, thanks.
It always stuck me as somewhat ironic that it is difficult to source TEA in Britain...