I have only had a F+F sent over from the States, again this was using USPS who charged $67.00, but as said, that was for a F+F only.
I have however heard of some horror stories unfortunately as mentioned above, ask the seller to mark all documents that the bike is a gift and its value is sub £30.00 in value....although of course, Customs arn't silly
This unfortunately is another example of how we get shafted in the country by import duty, last week I posted a £300.00 F+F to a chap in Australia, I was concerned about him being hit his end with import duty as the terms and conditions of carriage stated that if the recipient does not pay the duty, it would be returned to the sender (me) with all assosiated costs to be paid by the sender (me)
The buyer quickly responded by confirming that in Australia they are allowed to bring in $1000.00 Austalian Dollars worth of product (about £500.00) before any import duty comes into play
Good luck with it but from what I understand, its a bit of a lottery if you get caught or not