I will try to explain in English
Meter box:
The two little boxes to the (circled in blue) right of the meter have 3 pairs of tails (cables) going into the boxes, which consist of 3 live going to one box and 3 neutral going to the second box, as below.
1 pair are coming from the meter
1 pair go out of the meter box through the hole on the right into the house
1 pair (the thinner ones) go to the old white(ish) wylex fuse box – Does this supply the garage?
My main concern is you only have 1 pair of tails (cables) going into the house as described above and I cannot physically see from a photo how the two consumer units are wired from one set of cables. If I was to hazard a guess, there is a junction splitting the cables to supply each consumer unit from one set of incoming tails or the original house consumer unit feed the extension consumer unit from one of the fuses (MCB’s), as I say I’m just guessing.
Lets look on the positive side and say the extension consumer unit does indeed have 25mm2 tails (cables) supplying electric to it, then a charger could be installed on the same wall as the consumer unit, which would fall under a standard install by Motability. You could request the non tethered Ohme E-Pod and tick the option for 8m charging cable, which hopefully would be long enough, if not you can buy a longer one yourself.
On a negative note, if the tails (cables) supplying the extension consumer unit aren’t big/powerful enough to supply a charger, you are looking at taking a new supply from the meter box in the porch, which is not the end of the world trust me. However, best option would be to contract an electrician to do the job rather than paying top dollar for a non standard install by Motability cowboys. The same applies if you want the charger in the garage requiring a trench dug.
You never sent a picture of the electric supply cable going into the garage, as it may be suitable!
I would love you to take the cover of the extension consumer unit and send a picture, so I could give you a more definate answer BUT, you have got to feel confident and someone decided to put coving near to it, which may make removing the cover somwhat awkward! I bet you live to far for me to pop in and take a look?
Anything that isn’t clear please shout!