Scottish and particularly Welsh gold has always attracted well over spot if it is authenticated. The main reason being that we don't really have any mines producing any gold due to the strict enviromental controls and health and safety issues that running a mine involve.
Any nuggets or gold dust offered is usually the result of panners finding the gold in streams, damned hard work for the amount of gold collected, and this reflects in the prices that the gold is offered at.
Welsh gold also has the added value of the association with the Royal Family, gold from the Clogau st davids mine (which closed in 1999) has been used in the wedding rings of the Royal Family since the wedding of the late Queen Mother. The cottage jewellery trade in wales buys up the vast majority of the panned gold from the area, so, if you want some you have to pay well over spot to gain some or else go and pan it yourself.