i have just purchased vol 1-30 on amazon.co.jp. it worked out at a reasonable £53. there will be import taxes once it comes, perhaps another £10-£15 including the rip off clearance fee that couriers charge. (if amazon charge clearance fees, never used them for international purchases before)
so its not too expensive to buy this way. i was expecting to pay more.
so, all in probably £60-£70, as a rough guide, for others who might want to buy through amazon. i shall update for reference for others later on