Firstly, thanks to all for your helpful comments so far. I have a couple of things to add:
I am still keen to salvage something from this image if at all possible - especially as, with the weather like it is today, it is almost impossible to imagine Manchester in the sunshine again! But this kind of debate is also helping my general education on these matters. I have recropped the original image - close in, rather similar to Luis' 2nd cropping suggestion, but losing all the gear. Unfortunately I cannot work out how to post that image with this thread without making a new link to a resubmission (or a link to some other web space) - so how did you do that Luis? I want to get further feedback here before uploading another image likely to be rejected.
Also, when I look at my new cropped image, even though it still shows off the bright red elevators nicely (and the contrast with the blue of the fuselage is basically the motive for this shot), I become concerned that it resembles too closely another image that I already have on the database (see below).
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Photo © Paul Markman
However, this photo is of G-WWBB, whereas the crop we are referring to is another airframe, G-WWBM. Therefore I would also be grateful for your comments as to whether the obvious similarity between the 2 images would mean that it would be likely to be the cause of a rejection, irrespective of whether the screener thought the new cropping was acceptable. Or, as they are different airframes, does any similarity becomes irrelevant. Or, finally, should I just give up and put it down to experience?
Clear as mud? I hope so.