I am looking for some pointers to ship a omega box set+paper to the UK.
is it safe to ship the box set+papper (no watch) to the UK withouth custom problem? How much would shipping cost is? and what are the shipping methods?
UK custom is pretty lax. You should not be worried shipping the box and papers. Use USPS Global Priority Mail if you're in the US. Tracking provided at affordable cost.
Declaring it as gift would be a wise choice. Don't insure your package but register it for tracking. Value... anything below 100USd and above 20USD. This is just a rough guide.