The oil in the coil housing is an insulator, but its only actual purpose is to provide a thermal path to the outside world. The coil doesn't make use of the electrical insulation property of the oil in order to function (unlike the insulation on the wires, which it does need), only to keep it from overheating. This means a little oil leaking out isn't an issue in itself. However, now that it has forced its way out of the formerly-sealed can, more oil can leak unless that path is located and sealed.
Where there might
be a problem is if the heat due to the current having run through the coil for two hours[*] continuously, rather than only ~half the time when the engine is running, caused insulation on the wires to crack. However, that is unlikely since the remaining oil still managed to carry away a lot of the heat. So, the decision isn't a simple as buying new coils. You have to decide between the estimated future reliability of an original made-in-England Lucas
coil that was hot for a period of time and that leaked some small amount of fluid (nb. I assume the leak was small; if not, let us know), and the hoped-for reliability of an aftermarket coil made overseas.
[*]Your coils are 4 ohms each and are in parallel so they each drew 3 amps from your 12 V battery
. This dissipated 36 W ea. that the oil needed to carry to the can and from there to the air. If it was a 12 Amp-hr. battery
that heating went on for ~2 hrs. before the battery