Wasn’t either Portsmouth or Hamble factory and the airfield site seperated by a railway track with a footbridge?

I would agree with above that a factory site or even an RAF ASU airfield with dispersed sites seems favourite, some of these had lines very close by and some (such as St Athan) on the station itself.

Looking at an old map from Hamble – it might be where I put in the red circle with the question mark….
http://www.doghousecrafts.co.uk/handdaf/ham/hammap.jpg

I may be way off the track here, but i seem to remember seeing years ago in Aircraft Illustrated pictures of a Shack crossing a rail line on the runway at a base in Ireland, maybe there?

…this one from Ballykelly?
http://www.nrf37.co.uk/Shack/

Here is an article about 11 railway-runway crossings
RAILWAYS CROSSING RUNWAYS: A WORLD-WIDE UPDATE…
http://carendt_backup.gully.org/scrapbook/page93a/index.html

Just found this from an auction catalogue
http://www.sheffieldrailwayana.co.uk/catalogues/1103/telephone.htm
It is No. 484

…and by looking around I came across this from Australia
http://www.airwaysmuseum.com/WYY%20rail%20crossing%201.htm

Found this
“He has taken part in a large number (61) of operational sorties. An efficient and capable wireless operator, his fine example has done much in welding together a first-class crew”

here:
http://1914-1918.invisionzone.com/forums/index.php?showtopic=65436&st=25

HE-J is mentionend in connection with a
Westland Whirlwind
P7116 HE-F *NOTE: This aircraft was later re-coded as HE-J
and a
Hawker Typhoon
MN823 HE-J
http://www.rafcommands.com/forum/showthread.php?33-263-Squadron-individual-id-letters

here it is LN-DAN

Thank you so much!

Have also first thought of BOACs Liberators
http://webcache.googleusercontent.com/search?q=cache:-sQvDS7Bx04J:www.rafb24.com/index.php%3Foption%3Dcom_content%26view%3Darticle%26id%3D4588:liberator-ii-for-the-raflb-30%26catid%3D29:the-b-24%26Itemid%3D41+BOAC+Liberator&cd=9&hl=de&ct=clnk&gl=de&client=opera&source=www.google.de

A nice vintage ad http://www.dartfordarchive.org.uk/technology/magnified/vickers_ad.htm
and some details http://www.dartfordarchive.org.uk/technology/engin_vickers.shtml