VAT & Duty…
Take the frame price, add 4.7% for duty on a bike frame, then add the cost of shipping, then add 20% VAT on the whole lot. On top of that the courier in the UK will slap on a rip off handling fee (varies but typically between £5 and £20). That’s your total price.
http://www.hmrc.gov.uk/customs/post/internet.htm
https://www.gov.uk/trade-tariff/headings/8714?country=&day=22&month=9&year=2014
And it doesn’t make any difference if it’s second hand. It’s a purchase from overseas, that’s all that counts. Marking it as a gift only ups your allowance to £36 so makes no difference to a bike frame.
p.s. HMRC can decide to value the frame themselves and ignore the declared value if they don’t agree with it.