[UK] What should I be doing?

I've recently graduated from a top uni in the UK (Imperial College), with an engineering degree (BEng). I didn't apply to many places during my final year so I didn't get any job offers, partly because I didn't think I'd graduate with a good grade so it'd have been pointless, but have been applying to finance/banking related jobs in the last few weeks through my university's careers page. I've interned at a BB over summer but it was a technology role, not where I want to be in the future.

My question is that since most BB firms won't let you apply to them unless you're on a degree course already to their summer internships, and since going straight to graduate roles is nigh on impossible, what should I be aiming for right now? Are there any additional resources UK people in my position are using to apply to places that they could shed light on? I want to waste as little time as possible on finding work to avoid having a blank gap on my CV.