Help Shipping a 1903 rearsight from the US to the UK

[waco16]

I suppose it makes sense imposing rules and regulations for such things, but they don't seem to be applied sensibly.
A barrel, bolt, firing pin etc you would understand - but a rear sight from a 100 year old rifle?

I've just received another small package from the US - an original blued stacking swivel and band for my 03A4.
Bought from a seller I've dealt with before on that auction site, and delivered with no problems