Having been around Europa's for 40+ years, market value increases have significantly climbed in the last 10 years.
As with the passage of time and availability, the Europa has established itself a "sport/enthusiast's" vehicle...thus with it's racing heritage pedigree, there will always be a brand value included.
If we go back say, 20 years...a clean, running, low mile original would fetch 10 to 15k...
On average add one thousand every year...(per the Hagerty guide)
If you consider options...JPS, Special w/ 5 speed, weber head, add a few more bobbles.
There will always be that exception, however if I were to consider the above mentioned cars...each have a distinctive merit to them. I would value them closer to 35 to 40 range, with the black special getting the nod due to it's maintained unmolested condition and very low miles.