It has come to my attention (not mentioning names of course, KATHY) that Brits secretly snicker at Americans when we say 'pastel'. Apparently, we say it funny. Pa-STELL.
If you are in London, be sure to say it this way: PAH-stl. Barely give that second syllable any attention. All the emphasis is on the first. And of course make your A sound like an O. There, you have it!
(That's ok. Americans secretly snicker at how Brits say "Aluminium".)