Looking at the picture the obvious sore thumb is the grommet not properly protecting the grey cable at the bottom of the switch!
That is an isolator switch and a 50A MCB, there is no RCD protection at that point unfortunately. Had the SWA cable gone all the way that is not an issue (if punctured the earthed armour shorts out and makes it safe), but care is obviously needed in case the cable is damaged (so should be at least 50mm back from any wall surface if hidden, etc).
Has the garage CU got an RCD? A photo of it might help.
From the 16mm estimate of the SWA cable it is
probably 6mm, as the T&E is also
probably 6mm to match, but doing remote investigation is obviously not an exact science. If so the current limit for 13m T&E + 30m SWA run is
probably around 34A based on voltage drop.
However, a 50A B-curve MCB for short circuit protection for the cable might not disconnect fast enough to meet the wiring regulations, it would need checked (the Zs measurement mentioned before).
So probably you could use a higher trip level breaker, such as a 16A C-curve, 20A C-curve, or 32A B-curve, but it would mean:
- Measure the total earth fault impedance Zs at the garage CU
- Check feed cable specifications
- From Zs check the cable feed breaker is acceptable
- From Zs check what final breaker is acceptable
- Checking the wiring of the garage sockets are rated above 16A (in case they are in 1.5mm T&E for some odd reason)
Your best plan would be to get a professionl electrician in to check the details before changing anything.