And what does CAP 413 give as a guidance on a "quiet" frequency that may just have several/many data-linking capable aircraft....... It is very easy to assume. If it is an unusual or long request, I would much prefer a pilot to say "request" and wait for a "pass your message", even more so as I'll be scrabbling around to see who has a scrap of paper and possibly a pen that works so I may even write some of it down.
I definitely offer the same service in reverse......