Hi Steve... Actually in my opinion Wetsnapper suggestion is just about on the money.. Reference to HDR and Tone Mapping has no meaning at all in this situation...
I thought I was going mad for a bit, thank you
To make it a bit easier, I actually exported my pano as cube faces then put it all back together as pano.. As long as no windows are cropped into a different face, it works fine...
This was where the idea of creating a separate pano that could be used over and over again came in.
If, say all of your panos are created facing the same direction, the background - outside- pano can just be copied and pasted into each interior pano and masked off, so only the windows are visible. The background should match up on all the interiors. No need for warping, converting to cubes or aligning horizons etc etc. As you said as long as the windows don't jump the gap you're fine...If they do you can set up guides so they go out at exactly the same point at each side of the pano. Another advantage is you're just working with one image, not 4 different ones.
Yet another advantage is that if you need to put a different background in, for any reason (a real pano, once I've shot one in my example), it's just a copy and paste job which takes a few seconds.
For getting my kit out of refections, I've also found converting to cube faces is the way forward for any PS work, so much easier to see what you're actually working on, rather than trying to join the curves in a spherical image. If a shadow from a tripod goes across the join you have to remember to look at the spherical pano again afterwards and make sure there are no ugly patches/mismatches.