I live not a million miles from the posted location. I haven't seen a C17, though I've seen quite a few Avro RJ. I appreciate they're substantially smaller than a C-17, but if someone's unfamiliar with their shape there might be some confusion.
Smiliner: BAe 146/Avro RJ Operators - United Kingdom
Problem with that is when I tried to check who operates Avros out of City, there seem to be a lot fewer than there use to be.
I will keep my eye out though. And if I spy a C-17, I'll post my humble apologies in the thread.