Help deciding Whether to decline/accept my offer

I applied last October for Computer Science with the following predicted grades:
- A* Maths
- A* Computer Science
- A Further Maths
- A Chemistry
- A EPQ
I only received one offer, from the University of Sheffield (AAB) I was rejected from the following t Universities for the following reasons:
- University of Bath: Came very close but too much competition
- UCL: STAT too low (71)
- University of Imperial: Failed post interview
- University of Durham: Predicted grades too low
I believe I can get even higher grades and I know my Personal Statement is very strong because I got an Imperial Interview.
I don't know what to do. Do I try to get a better university through clearing? Should I go to Sheffield, despite my grades being far above the requirements? Do I take a gap year and apply with actual grades? Any advice would be so so helpful. <3

Try to get better grades in the real A Level. See through clearing if you are able to re apply for any better unis
If not, gap year is available. Gap year is a great way to get work experience or a job and save up.

how likely is it that a better uni shows up in clearing though, for COMPSCI, so competitive. Also I'm worried about rejecting my sheffield offer and then not finding anywhere in clearing and having a worse/no uni at all. I'll have to research into clearing more.

Not very likely....I think KCL AI would be your best shot if you decided to look at Clearing but we can't guarantee anything there either.
Next year, Imperial is taking TMUA rather than that problem solving test we did this year so you're gonna have to invest more time in prep as TMUA is a lot harder than that test (but not by a lot. It's closer than you think. Speaking from experience as I applied to Cambridge and they take it too).
Also, I know that the Imperial website says typical offers won't have STEP reqs attached but because you're a gap year applicant, they may give you a STEP requirement with your offer to make sure your Maths ability hasn't fallen off (I might be wrong here but my friend in the year above reapplied and got Cambridge Engineering and they gave him a STEP requirement with it, so I don't see why they couldn't do it with other courses and at other unis, especially considering that Imperial required you to do the STEP this year as part of the offer- I hate it so much rn. The questions you get in it are so horrible and I wish it wasn't a part of my offer requirements but it is what it is. Don't care about its difficulty but I'm just tryna meet the conditions for it).
Sheffield is a great uni so consider going there but see what happens on Results day first. If you've performed really well, reject Sheffield and reapply on a gap year.

Thank you so much, good luck with STEP it's absolutely ridiculous.

how likely is it that a better uni shows up in clearing though, for COMPSCI, so competitive. Also I'm worried about rejecting my sheffield offer and then not finding anywhere in clearing and having a worse/no uni at all. I'll have to research into clearing more.