Should I attend a biological sciences informal interview?

I've had an offer to attend an informal interview at Sheffield in a couple of weeks. However, I already have an offer from my favourite university and Sheffield will likely offer me a higher offer (or definitely won't be lower, at least).

So, is there any point attending, or should I decline to avoid wasting both of our time?

I I am sure I will put the other university as my firm. I am still waiting to put it down because I'd like to try and get an insurance offer too.

Have you visited Sheffield yet? If not, you might want to go to check it out, you might be pleasantly surprised. If you have, if you are 100% certain that Sheffield would be neither your firm nor insurance then sure, you can withdraw. I'd go, if just for the interview practice.

I went to open days at all the universities I applied to, I'm really torn as to whether I should go for the interview (I've never had an interview and I'm quite socially anxious), but I really shouldn't miss the school day unless it's really necessary since some semi-important things are happening.

It's so hard! I think I'll ask my form teacher tomorrow about it...