It sounds like you and I are in the same situation (funnily enough I’m also from the UK and am now living in Chiba).
I spoke with the Kickstarter team on Friday and had more or less the exact conversation you intend to have...
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I suspect if you request to switch to a digital copy instead of a Japanese copy they will be able to help. Otherwise, I think your best bet is to wait and/or pick up a copy on launch day.
I was a bit hesitant to do this as I plan on playing the DLC at some point and as my PSN account is registered in the UK, wouldn’t be able to download DLC for a Japanese copy without setting up a separate PSN account. I ended up just buying the deluxe digital copy from the PlayStation store (I’m just installing it now so that I can play it at as soon as I get home from work on Tuesday).
If you decide to go down that route, I found a webpage selling PS store credit about 15% off, meaning I paid £58 instead of the £70 it’s listed at.