G - B - C - Cm
The relative minor of G major is E minor, so going G-B is a preparation for a nice V-i "perfect cadence" into E minor. Nothing unusual.
From this perspective of E minor, the B-C is V-VI — a perfectly standard "interrupted cadence".
Within the first three chords there's been a nice chromatic voice going d-d#-e — with the C-Cm, this then reverses, so you have d-d#-e-eb. This gives the four bars a nice looping round on itself quality.
There's a probably a specific name for the Cm-G iv-I "plagal cadence" — eg I can think of pieces by Bach that end like that — but if I ever knew it, I've forgotten it.
All these elements would make sense to someone doing A-level music. But I do think the theory is just explaining why it sounds good to us, rather than suggesting to the composer what should come next.
Personally, I think that the important part, given that this is rock music, not classical music, is the inner voice with the chromatic steps looping round on itself, rising hopefully, falling plangently.