why not astia Kev?
Negative film isn't THAT bad, you already shoot B&W negatives and I personally don't have that hard a time holding up colour negs and being able to see what's on there, though yes, slides are MUCH nicer for that.
Maybe a trip to Japan is needed?
Kev, what about a bulk order from the states? A quick look at adorama says buying 50 120 rolls plus shipping works out about £3.25. You would need to add duty but when it's not for sale it doesn't seem too bad?