I just rang up my local depot, they said when your parcel tracking is at "awaiting payment of charges" you can go to the depot and pick it up and pay there without the mailed payment slip. All they need is ID that has your address on, and the tracking number.
It's nothing significant or out of the norm really, nothing to be concerned about. It's basically a secondary check that the amount is representative of the product, could mean the charge went up or down, or stayed the same, you'll never know.
Your charges don't sound right, did sfflab undervalue your case on the shipping info attached to the box? It sounds like you only got charged 10% + handling fee, rather than 20% + handling fee.
Nothing to complain about like, just curious.
Also still stuck in customs. I've had plenty of items at around the same value pass through our customs before, none have taken this long.
It will have to be released from customs before they will send you any letter about it, Parcel Force or whoever is handling it will pay the charge on your...