Hello jd01, glad to see another Brit in the mix!
So far I've got a S6 and a SS4 in-country without any problems at all.. Patti is good at wrapping stuff up so that the Royal Mail doesn't rip it to bits and lose the contents for you! Items come described as camping goods or camping tools, NOT big scary knife so go straight through customs.. I plan to get the DF when it comes out, even though a S6 is plenty big enough 99.5% of the time. I don't expect problems with it arriving (famous last words!)..
Enjoy the yard and grab a S6 when they return, superb knife- even in our climate! Plus Dan and Patti (and these guys here!) are good folks.