Declaration, Duty and VAT fees

I will be leaving for the UK on Feburary 18,2013 (next week) I have my fiance visa and will be marrying my British fiance on March 30, 2013. 
I have a question about getting through customs. In addition to my other baggage of personal use belongings, I will be bringing 2 guitars with me. One is a travel guitar in its own compact backpack--a Voyage Air-- and the other is a hardcase Takemine acoustic guitar.  They are under a year old and I have my US receipts for them. 
Will I have to declare these items and will I be subject to a duty tax of VAT on them? They are my personal guitars.   Thank you.

http://www.dutycalculator.com

I don't think you need to pay anything for bringing your own personal possessions in when you're moving. It never even crossed my mind to all about duty on the violin I carried in. That's quite different than if you bought something overseas on holiday.

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http://customs.hmrc.gov.uk/channelsPortalWebApp/channelsPortalWebApp.portal?_nfpb=true&_pageLabel=pageLibrary_PublicNoticesAndInfoSheets&propertyType=document&columns=1&id=HMCE_CL_000282#P163_19904

You must have owned them for at least 6 months.