Big4 vs IB Opinions?

Some Context: I've always wanted to go into IB but didn't really apply for any summer internships/grads during my final year of university because of my workload (which I regret).

I made a last minute grad scheme application to one of the Big4 for Advisory in London after graduating, and was applying for off-cycle internships (starting feb)/grad schemes in banking when they opened. I received my offer from this Big4 a few days ago and they surprisingly offered me a 2018 start date. They only gave me a 1-day deadline and I chose to sign the contract for financial security/ timing worked out for flat-sharing with friends in London.

My question is, should I carry on with my ongoing applications/should I apply to more, or should I give the grad scheme a chance and cancel my applications?

NB:
I think it'll be hard going in for interviews/ACs once I've just started working. There's also the issue of not liking the banking team/actual work once I get there, or not being able to convert the off cycle. The Advisory role may be enjoyable as it's from how others describe, like corp finance in IB but smaller deals and less intense.

I've also not really had any formal IB experience. I did a couple of FO spring weeks at bulge brack investment banks and an industrial placement year in FO Asset Management at another BB.

What would you do in my position? (Apologies for the long post)