Basically Im considering doing the same as you so Im just gonna give you my opinions and thoughts.
Firstly I would say definitely finish this year if you can- It proves that you can get down to studying and get through and also other universities/other course may want to see your grades from this year and you want them to be good enough to actually continue your education.
Secondly, your right when you say theres no point in just starting another degree in september- You need time out to sort your head out and figure out what you want. I understand the situation with your family, to be honest I cant really imagine moving back home for a year, but you say you are homesick so this makes more sense for you. Is there another relative you can live with back home? Grandparents, aunt etc? If you work, you could always look into a flat share? I already have a house for next year in my university town and I have a job so I would be tempted to stay there and not actually go home but Im not sure about logistics yet.
Regarding student finance- you are given basically a 'free year'. This basically allows you to f**k up your first year without suffering any financial consequences. (You would have to actually complete the whole year- if you drop out now, you would have to pay back some of your maintenance loan and comtinuing paying halls rent even if you are not allowed to continuing living there.) Tuition fees are never repayable until you earn enough money as far as I know.
So basically, as long as this is your first year of your first degree you wont have a problem getting finance for a full second degree. But anything after that will be harder.
Personally, Im definitely considering deferring a year and probably staying at the same uni although Im tempted to leave as well. I have a good social life, a few really good friends and a bunch of acquaintances- maybe think about what you would end up missing about the uni your at? Are you definitely homesiick enough to leave this uni in particular? Because it would be a lot easier and a lot less stress, to take a year out and return to the same uni doing a different course- often all thats needed is you write a mini personal statement to the other department and have a meeting with them saying what you wanna do. A year out spent with your family might make you realise you dont want to be at home?
Otherwise, have a look at unis closer to home, and I would definitely recommend having a year out to decide what you want. When I picked my course and uni for this year I spent about 5 minutes choosing it- I now wish I had had a year to properly consider it!
Let me know how it goes, PM me if you want - were in similar boats so be nice to how someone else is handling it!