Wow ! A 2014 Gold Five Ounce Britannia (I think a 500 Pound Face Value coin) went for 37,000+ US Dollars last night at BowersMerena Galleries Auction last night at the NYINC. Many of the Brit coins went for large amounts as well. The small six coin gold set of same year went for 10k or so by recollection.
This 2014 Britannia seems to have achieved a life of its own and even the lesser silver brethren do pretty well on the secondary market.