To answer your particular question with regards to 'what font is used on the East Midlands Trains Destination Display?', I have no idea, but I know how I would approach the problem:
1) I would start by taking a look at the LCD fonts available at dafont.com.
This link takes you to a list of open-source and 100% free fonts that look like LCD displays (bear in mind there are two pages) and gives you a preview of them using the text Derby, Chesterfield and SHEFFIELD. You can then identify the font most similar to what you are looking for by eye.
2) If none of those fonts match,
this link includes those fonts that are free for personal use or not free at all (shareware, donationationware etc) in case the first link doesn't provide you with what you wanted. You can check the license of each individual font on the far right hand side of the fonts entry in the database above the download button.
3) Another tool that is useful if you have a high-quality image of some text in the font that you wish to identify is
WhatTheFont? tool made available by myfonts.com, and if that doesn't identify it there are lots of font experts ready to have a go in the
WhatTheFont forum.
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Also, just in case I've missed the point and the destination display you speak of is one of those 'flip character' things (
flap display) (though I havn't seen one in years), try looking at the following free fonts:
Stencilie
JD Eugenia
Aero