In most cases there aint much a sender can do once a registered but not insured package went lost after it went across the border.
I will always remember when I sold a record to the UK and it went lost in the shite British post system. The buyer contacted the BP, they searched for it, found it, testified that to the worried buyer..only to tell him (in fact her) a week or so later that it went lost again! Unqualified idiots.
No refund, nth.
It was send registered. But the German post said its not their responsibility once it has left the German post system. And rightly so of course.
Well, to cut it short I was made/held responsible (by the buyer) and to safe myself from more negative emails and such that started coming my way from the frustrated buyer I ended up paying back/refunding her 250 UKP out of my own pocket!
So I as the seller lost out on both sides, money and record!
Since then I am always (a-l-w-a-y-s) nervous when sending to the UK.
The German post is one of the best in the world though, fast and almost 100% reliable. Hopefully for some more time to come...I am afraid it will change over here soon too though...
Marc