well the £37 cost for each figure may obviously change from day to day based on what ever the exchange rate is at the time. but customs is usually 17.5% (and another smaller percentage but can't remember what).
customs are usually charged on items of £30 or more (£18 if its marked as a gift) and it would be based on the £37 not the £7

personally I don't have a problem paying customs charges (well small ones :D) but it really pisses me off when Royal Mail/Parcelforce add theirs. They very kindly pay your customs charge then charge for that - Parcelforce (with a parcel that size is at least £14
I would say if you bought all 3 (and this isn't including the shipping from Japan as I don't know how much that would be) you'd be talking £55-60 a figure
PM on its way to ya!!