Found a stray kitten in Mallorca, is bringing her home to UK actually the humane choice?

My partner and I were on holiday in Mallorca and found a stray kitten on the land of the Airbnb where we were staying with friends, she's somewhere around 8-12 weeks old. We had to leave yesterday, but we're seriously considering bringing her home to the UK with us and are in contact with a cat rescue who has outlined the process, costs etc & could support us through it.

I've been so upset at the thought of leaving her but keep going back and forth on whether this is actually the right thing to do for her, and I'd love some outside perspective.

Context -

When we found her she was alone and quite timid at first but warmed to us very quickly and got attached. She'd hang out with us all day by the pool, and all evening while we had dinner and drinks outside. One day we went to the beach and left her behind, but she was in the same spot when we got back, meowing at us.

We let the Airbnb host know as we left. She said she couldn't take her in as she has a dog, but seemed to think the kitten would be fine at the Airbnb (there was a language barrier so this wasn't totally clear). I think she'll probably be okay there since she's so friendly, and I'm hopeful people will feed her, but obviously that's not guaranteed, which is a worry.

We also tried hard to find her mother or siblings. We left her alone for a long while at first, but she kept finding her way back to us and we couldn't locate any other cats nearby. One day an adult cat did turn up, and we gave them space to see what happened, but the kitten was terrified and wouldn't let it near her, so I don't think it was family.

Temperament-wise, she's completely cuddly and very attached to us, playful too, but more on the cuddly, clingy, sleepy side. She'd follow us around and sleep on us for hours.

The case for bringing her home -

• No guaranteed food where she is now
• She likely has fleas, no vaccinations, not neutered
• In the UK she'd have a safe, warm home with guaranteed care

What's worrying me -

• In Mallorca she can roam free, in the UK she'd be in a 1-bed flat in London, about 45m² with high ceilings and a fairly big open-plan living/dining room, is that too little space? (I'd want to try harness training her so I can take her outside, though I know that's not a given, especially as she'll be older by the time we get her here. I'd also make sure we have lots of enrichment and vertical space to climb.)
• I work from home so I'd be around a lot, and at least one of us is home most evenings, but we do often go out at weekends
• By the time we can get her here (vet checks, waiting period, flights) she'll be quite a bit older than she is now, so I worry she won't adapt as quickly
• The journey itself (vets, cattery, flying, drive) will likely be really stressful for her
• Money's a bit of a worry, it's not cheap and we're not rich, but we can use savings to cover it and our monthly income could support a cat. If anyone has experience bringing a stray home from abroad and ran into unexpected costs, that would be really helpful to know

Basically, I can guarantee her safety and a cosy life if she comes to the UK, but I'm not sure that means she'd actually be happy. Has anyone been through something similar, either bringing a stray home or deciding not to? Would really appreciate any honest input, good or bad, I don't want to act with my heart and end up making a decision that isn't best for her.