Thanks for the offer, but I'm in the UK so shipping would be excessive
Luckily the place I bought the formulas from are happy for me to return them and they have the company in xl, and as they're based in the New Forest, (a very nice area of the UK and one of my girlfriends favourite areas, about 2hrs drive away), we're gonna take a ride out Saturday and swap them over.
The problem seems to be that while the large bindings go to a UK10, UK11, they only go to a Eur 44.5. My UK10 32 lashed are a Eur45, which explains why they're tight. To be honest they may be useable, but will almost certainly damage my boots and will get frustrating having to wrench my boot out all the time.