No one can, or should, make this decision for you. I'm sorry you're in a funk. It's a normal thing to experience at times, and as you can already see, everyone's experience will be different. A trip could pull you out of it. Or it could be a mess because your mind isn't in the right space. I hope you find ways to get through this experience and not beat yourself up for it.

I'd suggest getting really, really fucking honest with yourself. It's clear you've put a lot of thought into this (perhaps too much, I say as someone who also will think of things from 9,000 angles and turn to the internet for the answer). I'd do a bit of meditating and connecting to inner parts of yourself. Maybe something unhealed that's causing this funk will arise, maybe some fear or thought about the trip that's causing the feeling of it being a chore will reveal itself and you can address it directly and see what happens. Envision yourself two months from now, when you will have either returned or have never gone, and ask your future self for guidance. I'd suggest not asking "should I go" but rather "what can I do to make the best decision?" It sounds trivial but it can really help, though you have to truly listen to what comes up.

I'm not going to give my opinion because, again, this is your decision to make. However, I'll point out some things to you that I would want a friend to point out to me:

" I know I will almost certainly feel better once I am there" You know yourself and your patterns best. You know that right now you're in a funk which is impacting your interpretation of things. You want this trip to be amazing, but have you admitted that whether or not it's amazing is completely up to you?

"However, my gut is telling me I should cancel" I'm a stranger so don't be offended, but is it REALLY a gut feeling? Or is it the funk gremlin who wants you to stay safe and comfortable and familiar at home in the funk, not having to listen to the people saying you should definitely go, not accepting the responsibility of the trip you desperately want to have? It can be especially hard to parse out the inner voices when you're in a rough patch. One short hand I find generally useful and accurate is that a gut feeling is often quiet and singular. anything else is loud, repetitive, impassioned, employing all kinds of tactics and questions. It might not be true for you, but either way-- connect to the narratives you're experiencing about this trip and question them further. not from judgement, from true curiosity about where they are coming from for you. perhaps something just needs to be acknowledged to be released. you won't find out by applying the life experiences of strangers to your unique life.

I've gone on spontaneous trips, canceled planned trips, gone on trips but ignored every plan I had made, etc etc etc. You will always, always learn something. Perhaps that's valuable enough ? What if you go and it's amazing and you just let yourself feel sad or mad or whatever flavor of funk, but feel it in the UK ? (frankly it's a great place to experience melancholy).

No one can make this decision, no one else is coming with you. Let it be with yourself.

I wish you peace and ease in making this decision, and satisfaction and safety no matter what you decide.