@kezo Thank you so much for taking so much trouble to give such a comprehensive reply. In all honesty, I am still struggling to understand the vast majority of even your simplified electricians language. I am clearly a lot thicker than I thought ?
The main meter cupboard has a door on it identical to the one in Stuart’s photos and is also recessed in exactly the same way, but in a thick internal stone wall (it was the outside of the house until the porch was added). There is a considerable distance from the main meter cupboard to the garage. To give some idea of distances, the main consumer unit is only around 6 feet from the main meter box, but through an 18 inch thick stone wall. The box in the extension is the length of two rooms away from the main box (I have absolutely no idea how or where they are connected). Where I would want the EV charger (if it was in the garage) is the equivalent of another two rooms further away again from the second box (so four rooms away from the main one and the equivalent of 5 rooms away from the meter box). As I’m sure you’d understand, I would not want visible cables running that sort of length either on the outside or the inside of the house.
The only way that I can see it working would be if any work required within the main meter box and the main consumer unit could be restricted to within those boxes only, with nothing required external to them. I could potentially live with cabling from the box in the extension, as it would either just be through a brick external wall (if the charger is outside) or through the utility room and then the length of the garage (if it’s fitted in there). My garage is very big. I can get two large cars in it and fully open the doors of both, whilst still having storage around the garage end and edges, so you can see why charging in there is preferred. I always park in there as there’s an internal door into the house from it, so my wife can transfer in and out of the car from her wheelchair without going outside. That said, the potential fire risk of charging a EV in there does concern me a bit.
So, I suppose ideally what I’d be really grateful for is a simple yes or no answer as to whether the scenario described in the last paragraph (i.e. the only external cabling work being from the box in the extension to the charge point) is potentially possible? If any cabling is required from the main meter box or the main consumer unit, then I think it’s a no-go. Hope that makes sense and, once again, sincere thanks for you time with this.