Yes I was thinking of going there thanks.
I know I wouldn't ask or expect a retailer to split a par of boots, but at a factory every boot is simply added to a matching size to make a pair. Logically they simply return each boot to the appropriate size coming off the line. Then it gets matched back in.
Its because they take a pride in ensuring a proper fit that I assume they would do this?
I was unaware of any difference in my feet (beyond a bunion on one) until quite recently. Though I gather that lots of people have different size feet (maybe not a big difference). Mine is just a half size I think.
A quick phone call to the factory will confirm whether they are prepared to sell you a split sized pair or not.
If the information on the website below is still correct the only boots manufactured onsite at the factory in Richmond these days are the made to measure boots with all the rest being made in a factory in Italy. Prior to seeing that I had understood that the Military and Police contract boots were made in Italy but the walking boots were made in Richmond.
https://www.timeoutdoors.com/Blogs/Andrew-Risbey/January-2014/Visit-to-Alt-Berg,-the-Yorkshire-BootmakersThe off-the-shelf walking boots are all made in Treviso, Italy (under close supervision from Richmond!), which is also where all of the leather is sourced.
The only walking boots still made in Richmond are made to measure boots - but this is very unusual given that the standard boots come in English sizes 3 - 15 together with 5 width fittings, making a total of 115 different fittings! Made to measure is really a last resort for people with very unusual feet or injuries etc.
I also have a ½ size difference between my feet when weighted and ended up with a same size pair but did find that I had to go up a full size on my actual measured size to achieve what feels like an extremely comfortable fit to me. I've seen others reporting exactly the same thing as it seems that Altberg do like to fit their boots very snugly indeed - perhaps too close fitting for some including myself.
Whalley Warm & Dry will be best placed to advise you once they have measured your feet and you've tried a few pairs on. Trust your first impressions when trying them on as you will immediately know when they feel just right and after 10 minutes wearing them and wandering about you should not even be aware of them being on your feet.