Applying for 2 courses at 1 uni

This will be down to uni policy, some unis will only make a single offer per candidate (I suspect most really but I only know of a couple offhand that specifically mention this) and so would ask the applicant which course they want an offer for (assuming they meet the requirements for both). Applying to multiple courses isn't going to increase your chance of getting offer - I suspect particularly for such similar courses, if you meet the requirements for one you'll probably meet them for the other, and vice versa if you don't meet the requirements.
I'd recommend sitting down and thinking about what course it is you actually prefer and just apply to that one. You can then write a more focused personal statement and engage more directly with that subject in your wider reading and exploration of it

do you know if I might be able to find info on this policy on universities websites?

My primary reason in applying for both would be that only 4 unis offer a Social Sciences degree, and out of them I'm only wanting to apply to Sheffield and Manchester, so figured I'd be best using my other applications for similar courses. If I've written my personal statement focused on Criminology as a social science, as well as one or two other disciplines I'm interested in, would this be suitable?

Thank you!

Is there a reason why you only want to consider Manchester or Sheffield?
Are you more interested in a specific criminology degree or one that offers a broader range of social sciences?

I really like the modules that Manchester and Sheffield offer - I know that these can change from cohort to cohort, but not hugely. The other unis with social science degrees are York and Leeds, but I'm just not hugely interested in their modules. I also loved Sheffield when I went to their open day, and Manchester is not too far from where I live, so they seem like good options.

I definitely favour Criminology as a social science, so I wouldn't mind doing a solely Criminology degree, but I would love to combine it with politics and education in particular because there seems to be a lot of useful crossover, which I can do with Sheffield and Manchesters courses.

do you know if I might be able to find info on this policy on universities websites?

My primary reason in applying for both would be that only 4 unis offer a Social Sciences degree, and out of them I'm only wanting to apply to Sheffield and Manchester, so figured I'd be best using my other applications for similar courses. If I've written my personal statement focused on Criminology as a social science, as well as one or two other disciplines I'm interested in, would this be suitable?

Thank you!

Ah ok, if it's not the location of Sheffield and Manchester that's behind your preference, have you looked into Criminology courses at other unis as well?

Probably somewhere in their general admissions pages, it's hard to say anything specific as each university organises their websites somewhat differently.
Moving on from that, while I did say it's best to focus on just one type of course, this remark was sort of made in a vacuum of comparing two courses at one university. When you're looking across the universities in the UK, I'd recommend focusing more on the content of the course than on the name of the course.
A degree named "social sciences" probably has considerable overlap with degrees in e.g. sociology, social policy, criminology, anthropology, and similar areas. I suspect they would be used to people applying to their social sciences course who are also applying to those other courses - as long as you pick ones that do indeed overlap with the other "single subject" courses you're applying to (e.g. criminology if that's your main focus) and just write a PS focused around that, you would be fine.
By way of another example, HSPS at Cambridge also overlaps with those subject areas quite significantly (also notably, allows you to do some politics options too), but has an entirely different name on top of that!
I'd recommend generally aiming to apply to different unis that offer courses you like the content of which are similar in terms of content and thus adequately served by the same personal statement

Yes - I'm looking to apply for Criminology at Liverpool and Lancaster, but can't find a 5th uni I like enough to apply to, hence I may apply for both at Sheffield. Would I potentially be better just applying to a 5th uni I'm not really that interested in, rather than putting 2 applications into Sheffield?

I'm considering applying for both Applied Social Sciences and Criminology at the University of Sheffield, would they be able to give me offers for both (if I meet the grades) or can the only give an offer for 1 course?