I have to say I'm very grateful to everyone on this forum for educating me about electrical safety using these things. I am actually doing exactly what I intended to do when I first got the car, but I know what not to do and what to look out for to detect any problems before they've become critical. I realise how fortunate I am to have a robust metal-jacketed power point in my garage only 1.5 metres from the charging port in the car's normal garaged position, and that the house circuitry is very well designed with the garage lights and power points on a separate fused circuit. (The house fuses trip if a light bulb pops or you plug in a faulty appliance, which has always annoyed me, but maybe it's for the best.)
I had thought that I'd start looking at wall boxes, but right now I can't really afford that outlay, and the longer this goes on the less I want one. At least that's a solution if I do run into problems with the granny lead.
I haven't had to use an extension cable, but some people who have acquired suitably robust cables seem to be managing OK. I'm now seriously wondering what the guy up the street was doing when he had a (legally sanctioned) cable trailing across the pavement to his EV parked outside his mid-terrace house. (He's not doing it now, I suspect permission was revoked when they installed the village charge-point.) I had assumed he'd had a wall box fitted but for all I know he was using a granny cable and extension lead all the time.
I have a friend who has had a Leaf for two or three years. He told me he used the granny cable for a year when he first got it because of some delay with his wall box installation. I assumed that he'd also been using the village 50Kw charger to save leaving the car on the granny charger for a very long time. But no. The other day he started asking me about using public chargers as he's intending to drive up to Inverness and has never used one! He doesn't even have a garage and the Leaf sits in his driveway all the time. I don't know what power point he was using or if he was using an extension lead, but he didn't have any problems - he only got the wall box to speed things up.
So far I have only gone on one visit where I might have had to use the granny charger away from home. I could have got the car into my friend's garage all right, with a power point just there, but it was a plastic one and I was a little bit doubtful. However, the public type 2 chargers only 50 yards from her house worked fine, so I never needed to try it.
Anyway, as far as I can see, reports of serious consequences arising from using granny leads seem to be pretty rare, and I think their use is more widespread than people often realise. I don't accept that the majority of the public will ignore firm safety instructions if these are communicated to them clearly. The issue, as with the coiled lead in the OP photograph, is that these instructions are not communicated clearly. I have a number of appliances around the house and garage that came with pretty prominent safety instructions, including a 12v lead-acid battery jump-starting kit and a snow clearing machine with a small petrol engine. I read them, and I'd have been a raving idiot not to. But there wasn't a thing inside the case of my granny charger or the bag of my type 2 lead to alert me about any issues. Just some text buried deep in the MG4 manual, about the granny charger.
In l'esprit d'escalier, I think if I'd had the opportunity to talk to the owner of the coiled-and-taped lead, I'd have spoken to him in a friendly manner, pointed out the risk of over-heating, and suggested that he untaped the lead and made a habit of laying it out loose when in operation. We need more education, not banning things.