If you feel like taking a chance, Address the package to yourself, but but some kind of church's name above your address (as in, Joe Soap, c/o The Church of Blablabla, Number mystreet, mytown, county Aye right XY1 23Z)
I heard customs are somewhat loath to levy taxes on religious materials, and I do know one guy who got away with it (although, to be fair, it wasn't a guitar or amp)...
Would it be any cheaper to import via the Republic of Ireland, say through someone on here, then it could be passed to the likes of me in the north, then shunted over (cos it wouldn't be an "Import" then)?