I don't konw what has prompted your persistant "doing down" of current Royal Enfield models Dave, but it does get to be a bit wearing.
My Interceptor was an early one (second batch deliverd in March 2019), so I could maybe have expected that it would have more issues - that has been the case with early production cars / motorhomes I have owned.
There have be issues that have required warranty intervention, but all have been addressed promptly without hassle & non have rendered the bike unusable. The finish is good and, after 2 years 3 months & 8,000 miles usage, remains so. If anything happened to the bike, I would replace it with another without a moments hesitation - it does everything I require at the moment.
Every Interceptor/Continental GT owner I have spoken to while out & about has expressed the same opinions that I hold - these are very good "real world" bikes that amply meet the requirements of those who have bought them - and bought them in quantity.
WRT the Meteor 350, it would appear that, again, it is a "real world performance" bike at a great price that is ticking a lot of people's boxes. I doubt if your Aeriel single would perform as well as the Meteor - did you find that sadly lacking in the performance department last time you rode it ? If you don't like the style, a "Classic" version of the same platform is imminent. One of my local dealers (not the one I bought my Interceptor from) mentioned a couple of months ago that he had taken 29 deposits on them unseen. My supplying dealer has a demo now & mentioned that one customer who had put a deposit on one unseen rode the demonstrator, declared it to everything he had hoped it would be & completed the purchase.
Having just returned from a 3 week tour including Somerset, Devon, Cornwall, Dorset & Wiltshire, I wonder how you have come to the conclusion that the 350 is unsuitable for longer journeys - the general standard & configuration of the roads in those counties meant that, over the 1200 miles I covered, getting up to 60 for any length of time was challenge & certianly few opportunities for sustained speeds of over 70. I have no intention of ever adding to the congestion in Cornwall again !
Last time out on my Classic 500 I didn't exceed 65 mph over a 200 mile day out - no point pushing the limits in North Yorkshire with the proliferation of camera vans - so a bike that was comfortable at 60 mph A & B road speeds would have been no disadvantage.
The 350 also benefits from a 3 year unlimited mileage warranty, so RE obviously don't have you pessimmism WRT buld quality & reliability.
Before being so damning about them (without having had any recent practical experience of the marque), when you are able you could take one or both of them out on a test ride - all RE dealers have demonstrators, because, by and large, a test ride is all the sales incentive they need.