Well, of course delivery time & costs will also depend on how far you guys intend to drift away. So if you want one, get it before the UK sets sail...

But seriously, I find the standard ignition on my '89 ETZ251 very good, durable and reliable. Indeed, you have to adjust/clean/lube the breakers now and then, while if you have an electronic ignition that's not required. An electronic ignition takes away that hassle, and once set right, it will stay like that. In that sense, an electronic ignition is far more reliable - it always stays the same.
But on the other hand, you have to take off that engine cover anyway every, say, 1000 miles, to lube the chain & look at that. Casting a quick glance at the points, maybe pull a sandpaper through it & measure gap, is very little work (if the gap is the same, the pre-ignition is the same). In fact, I've ridden that bike now for some 26k miles, and I cannot remember that the ignition ever gave me any hassle.
I have had electrical troubles, but those were caused by the fuse box (corrosion/contact issues), and I would have had exactly the same issues with an electronic ignition that only replaces the contact breakers. So I feel that therein also lies a weakness of such systems: they still rely on an externally provided voltage (the battery + conventional charge system) and the original ignition coil to create the spark. So if your battery is flat, or poor continuity somewhere - no spark.
But, as Johan Cruyff said: every disadvantage has its advantage - because such systems only replace the contact breaker & condenser, it is very easy to keep those somewhere on the bike, so in the unlikely case of a failure in the electronic breaker system, it is relatively easy to recover.
Many other (modern) bikes, originally equipped with an electronic ignition, use another system which does not use a battery for the ignition. Such systems are also available for the MZ, but obviously more expensive, as they also replace the generator.