Then he might explore a year of interruption/intercalation/leave of absence. If there's no illness or underlying reason for taking a break, it may be harder to organise, but he might explore deferring going into 2nd year for a bit.
I'd be encouraging him to
finish this year, so he has the credit points "banked" for the future - either a return to his cyrrent course, a change of course, or a change of university. Also so he doesn't
BUT talk to his Personal Tutor about his long term plans.
it's just what is sort of expected as part of the whole education process
This is what frustrates or exasperates me - this sort of attitude. It's a pity - a university place is a privilege, and should be only for those who positively want to be there rather than anywhere else (for whatever reason) ... it's why I think a gap year, for people to work at a real life job, is very important.
It's worth someone (maybe not you, but you could suggest he talks to his Personal Tutor) probing what it is that's unsettling him. To get into Bristol, he's obviously achieved well at high school, and you say he was keen & excited to go. So what's changed? Is the work's that bit too hard for what he wants to do eventually (that is, he can't see the long term gain from short term pain), or maybe he doesn't like the independence of university-level humanities studies? Some children who do well at school do so because they are next-to spoon fed, and find the adjustment difficult.
Someone needs to help him work out why he's so unhappy he's thinking of dropping out. Adjustment to university is a challenge - we recognise that. It's why in most degrees, first year marks don't count towards the final degree result. He won't be the first to feel unhappy & unsettled.
To get through it, you have to work out why you want to be there, or reassess whether you do want to be there. THat's OK - his Personal Tutor will have dealt with this situation before, it's not unusual.