I don't know if I will regret transferring universities?

You've got to weigh up the advantages and disadvantages of both options. Think back to why you applied to Leicester in the first place - perhaps the course content suits you better, the graduate job prospects are better, they are giving you the option to do a placement year/ year abroad, etc. Do these outweigh the possible disadvantage of the busier city atmosphere?
Tbh, if it's a campus uni you'll be spending most of your time on campus anyway, and may grow to appreciate the convenience in terms of travel/ buying things/ nightlife/ accommodation options that Leicester uni's location offers. That being said, if you really hate the feeling of the area and don't feel comfortable there then perhaps it's not the best option for you - if you struggle to settle in it could affect your grades and health.
Did you apply to any other universities? They might be more suited to you
You're correct in thinking it's generally easier to switch straight after your foundation year since you'll be joining the new uni with all their first years as usual, however it is reasonably common for students to switch after first year too (it tends to get a LOT harder after this point though) so if you feel that right now Leicester isn't the option for you don't feel rushed into a decision. Many other universities may still accept an application at this stage, or you can stay at Hull for another year.

Hey, thanks for your very well written reply, really appreciate it.

Well, I don't really hate the area around Leicester, but it's just so buys and impersonal compared to Hull. The area around Hull uni really does feel like a student playground, as everything is so close together. Also, I just enjoyed the fact mostly this year that I could always visit my friends houses who were pretty close in walking distance and currently I live in a street that has all the shops outside and is closest to uni.

The problem is that I can't guarantee I would be living close to uni or in this same street next year. Heck, I'm even afraid I might not see my friends next year or that we would drift apart.

And thinking back now, the reason I applied to Leicester was because I just didn't like the idea of living in hull city after graduating. I don't like hull as a city, but I do like the area around the uni a lot. So I thought I'd move back down to the midlands and just go to Leicester since I get the impression that it's a nicer city.

If I choose to stay in Hull for another year and then decide to transfer next year, I'm afraid I will lose one year worth of funding from student finance. Also when you transfer from first year, I heard it's hard to do because the uni wants you to give them a legitimate reason to transfer and you need a very good reference? It wouldn't be based just off of a ucas application right?

The thing is, I have been building up moving to Leicester after Hull to go to a city I would perhaps like more,but yesterday I visited the leicester campus. I got a bit disappointed because again, the area around leicester just isn't residential and relaxed. Even though the campus is massive and looks really nice.
You're right though that I would spend my time around campus mostly and not around the surrounding areas anyways, so it might not be as bad as I think.

But yeah, I am just scared of leaving all my relationships I have formed and giving up that nice feel that hull has around its uni.

I feel that the Leicster campus is just too close to the city, compared to Hull.

Edit: I have applied to other unis as well, but I just don't feel like going to them, and I haven't really checked out their campuses properly yet. I just feel so focused on leicester, I have applied to nottingham as well though, but I don't know anything about the uni. Also one thing that is quite off putting of Leicester's campus, is that it's like in front of a huge cemetery.

No worries

Hmmm, well I think if you moved to Leicester you would get to know the local area a bit more and discover things you liked about it (eg favourite coffee shops/ corner stores/ parks etc), so although right now it seems impersonal it might just be that you don't know the place. And as you mention, next year you and your friends might be spread out more accommodation-wise or drift apart, I'd say don't let friendships tie you to a place, there are always new people to meet

Hmmm, no offence but that does seem an odd reason go uproot yourself and move across the country haha! Most graduates won't stay in their uni city after finishing uni, you'll probably be looking for jobs anywhere in the country - and many people end up somewhere like London. So if that's your only main reason for moving, then if may be safer to stick with Hull since you're already settled in and know you like it there.

Transferring after first year does involve some discussion with the university before applying, they'll want to check your first year modules give you a good grounding for their second year onwards as well as whether they have spaces. There would probably be some discussion as to why you wish to transfer too. I've not gone through this process (but know some people who have) so can't advice much other than 'it's more complicated but possible' - although transferring now would be preferable. You're unlikely to have any issues with student finance unless you actually have to retake the first year at the new university - rather than transferring directly into second year.

I looked around Nottingham on their open day and their campus really is beautiful! I think the surrounding area was semi residential from what I remember (long time ago....) but the city itself was the standard busy city. I'd definitely recommend having a look at the other universities in your application before making your final decision