I'm selling my XTR9 grouppo (item # 7181695558) and got a question about
quoting a shipping price to the UK. I have no idea. Anyone have a clue
how to figure this?

You'll need to have the measurements of the carton, the total weight,
and the destination address. You can contact any shipper from the
USPS, UPS, FedEx, DHL, along with many other companies that handle
shipping internationally.
You will have to inform the recipient of the package that all shipping
costs, import duties or taxes, plus customs brokerage fees are their
responsibility, and handled and paid for at their end.
Now, the buyer can also specify a shipper. This means the shipper
would have
office in the country that you reside in, so they can contact you
directly to get the information on the package, and make arrangements
for pickup. When this happens, the shipper probably has a customs
broker hired on the other end to clear the package into the country,
and collect the fees from the buyer.
Now, don't forget one of the now classic internet purchasing scams
involves someone in another country offering you much more than your
asking price, paying with a cashier's check in the overblown price,
asking you to send the balance along with goods, then the check turns
out to be fraudulent, and you're left owing the bank(by law). Don't
fall for it.

Best regards,

John