Uni accidentally gave me an unconditonal offer but hasn't noticed?

Hello! I have been accidentally given an unconditional offer by a Russel Group University, I was trying to apply for their Bsc course, but was offered an unconditional spot on their Foundation course instead. I accepted, but when I check my UCAS, I have an unconditional offer for their Bsc course.
This is probably a mistake, but they haven't noticed and I received an offer letter with the contract and policy and all the emails you would expect. I know that they can revoke their offer whenever they want, but if they don't notice by the time I accept their offer, since that is a legal contract between the university and me, do they have to let me on the course?
Would appreciate any thoughts on what I should do.

Note that as far as I understand it, they can't change an offer once they make it without your permission so you can always query it without any fear. They shouldn't be able to change it even if it was an accident I believe (and it may not have been - if you are applying as a post qualification application for example). They can't "revoke it any time they want" - my understanding is that they could only do so normally if UCAS determines your application was fraudulent in some way in which case they can nullify it. However since there's nothing to suggest UCAS have any concerns about your application, I can't see that's a factor.
If it was an error then as I understand it per the above, is it would be up to you whether you want to renegotiate the offer with them or accept as is. That said if you applied for the foundation year because you are missing the relevant subjects I would strongly urge you to do so and take the foundation year - as if you start on a degree which you don't have the background for, it's very likely you will struggle immensely, and get poor results or fail to pass the first year. Which as well as potentially wasting a year of your SFE entitlement, is very damaging psychologically!

Thanks for your response. I would want to accept the offer as it is for the Bsc course, as the only reason I was offered the Foundation course was because I have an A in Literature despite having the sufficient grades for my course, (I am applying for Computer Science), so I don't think it would affect my performance anyways. I'll email them and see how it goes.

Did you take the relevant subjects required for that course though (I presume maths +/- further maths)? It seems unusual to be offered the foundation course in that case.
I assume you are applying with achieved grades in which case provided you did do the required subjects and have the actual required grades anyway I suspect what's more likely is they made the unconditional offer for the main course intentionally and the foundation course was mentioned in error rather than vice versa?
It's unclear from the context as we don't know what you A-levels you took, what grades you got in them, and if those are achieved or predicted grades, but I think from what you've said it sounds like the error may have just been in an email communication and not in the offer itself since by all accounts you meet all the requirements for the course.

I did have emails with them before where they said unfortunately since I have A star A star A, I do not qualify since the entry requirements are A star A star A star, which is why they were offering me the foundation course. I did do Further Maths and Maths, they just said that its that grade that means I don't meet the entry requirements. Since I think that's pretty silly since its a grade in Literature, hopefully the mistaken offer means I can argue for them letting me in the course.

I mean you didn't meet the requirements; A*A*A doesn't meet the requirement for A*A*A* regardless of what the final subject is in. So that is fair enough from their side.
In any event they seem to have offered you the main course and you've taken and done well in the relevant subjects so it might be worth just checking with them to make sure there isn't any confusion when it comes to registering in the new academic year.
I'm pretty sure they can't amend an unconditional offer if you've accepted it as effectively they made a contract with you and UCAS to uphold that, although there does seem to be some uncertainty on this and I can't find a clear statement on the UCAS site about it.