Customs Clearance

I'm sending off my Fiance visa app to NYC tomorrow morning *crossing everything*

I have a quick question regarding customs clearance.
My fiance is still in the UK, and I hope to be on my way over there in about 2 weeks.  I don't have a "set" day as I'm flying on an airline employee pass, so its standby.  I'm wanting to send my stuff across in advance (hopefully towards the end of this week) via air cargo.  How do I get my belongings cleared through customs.  Is it possible for my fiance to clear my items for me at LGW?  Or do I have to clear them in person.  I already have the C3 forms filled out minus the arrival date).

Ideally I would send all my stuff this week, and then just carry my bags on with me at the end of next week.

Thanks in Advance!

I spoke with HM Customs and Revenue's advice line, and they said that they didin't see any reason why my fiance couldn't clear my stuff for me.  So hopefully, things will go smoothly. *crossing his fingers*