It might be a bigger job than you think to go back to OEM, but without seeing your car I can't say for sure.
Spyder made a rear suspension conversion for the Europa and I seem to think I've seen at least two versions of it. IIRC the first version welded some brackets to your existing chassis to fit a top link above the driveshaft and to take the load off the driveshaft and allow it to work, they fitted rubber doughnuts as in the Elan. At the same time they offered a replacement chassis which would take either Lotus OEM or their own twin link arrangement, which sounds like what you have there.
They do have a version which uses a custom built rear hub carrier with a similar top link to their first version but with inboard joint being a CV joint instead of a rubber doughnut. They have a picture on their website showing it on a Zetec conversion they've done (included below).
So, where are we ? Well, if you have the original aluminium hub carriers then you'd need the driveshafts and inboard yoke to revert to OEM. If you have the full blown conversion with Spyder carrier then it is a much more expensive job to go OEM because you'd need carriers as well.
But why change to OEM ? Unless you want to take part in concourse competitions where originality is paramount, then arguably you have a more useful set-up. Several owners have deliberately changed to twin link designs and it also allows great flexibility in gearbox options because not all Renault boxes will take the side loads of the Lotus design through their output shafts/bearings.
Personally I'd retain what you have and talk to spyder about the possibility of modifying your driveshafts to take a CV joint. The doughnut was an odd choice at the time given that a lot of Elan owners were moving to CV or sliding spline UJ joint driveshafts to get away from variable quality doughnuts.
Brian