Laptop not delivered - how do I speak to a human to complain and resolve?

I ordered a laptop on next day delivery - waited in all day and it never arrived.

The tracking info on the account is out of date and says that my order will be delivered 3 days ago.

Phoning the customer care number gives me the exact same and directs me back to the out of date tracking info on my account, and no path to talking to a human. And no way of registering a complaint.

Emailing customer care did get a reply, but with no clarity on where my laptop is and again no means of registering a complaint.

So, Dell have £1500 of my money and I have no laptop and I'm being palmed off by switchboard.

Terrible customer service.

Does anyone have any experience of similar - and any ideas of how to get this swiftly resolved - and how to register a complaint so it gets taken seriously?

Thanks for ideas and support.