Brick terraces can carry several generations of wiring
Many streets in these areas grew around mining communities. So rows of brick terraces are common.
Some homes later became rentals or changed ownership several times. In practice, the wiring may have been altered in stages.
Meanwhile, garages and outbuildings can have later electrical supplies. Those additions may not match the age of the main house wiring.
However, piecemeal work does not automatically mean a full rewire. MPS checks what still works safely and what needs attention.