A pleasant surprise indeed Toby - sounds like you dipped in ok there paying the same as I have for one kit. My BII arrived yesterday, the total cost of that was £103 and I was charged £21.07 for that - £13.07 for VAT plus the usual £8 service charge. Of course you only have to pay that £8 if you have two or more kits.
From what I understand 'import duty' comes into effect once the goods value £135 and only then if the duty is more than £9.00 but how the duty is calculated percentage wise appears to be a mystery. It certainly appears sensible to order more than one kit at a time if funds allow.
I also noticed on my label yesterday that no postage is stated, only the overall value of the kit - '$119'. As I'm sure you're aware the VAT is calculated on the value of goods plus postage so it looks like that that is another small 'bonus' to our advantage.
I await with interest to see what Hannants will be charging for the BII once it's on the shelf, based on their current structure I would guess £130 - as you say quite a saving.
Long may the free postage remain
Regards - Tug