Advice regarding customer support

So I orded a relatively high end laptop about 5 weeks ago with the "premium" support. It took longer than expected to be delivered but that was okay. It lasted two weeks before it started giving me blue screen of death's with multiple errors. Became unusable very rapidly. Contacted customer support who decided that due to the multiple blue screen errors of different types that a repair (send engineer) or replace option was the best route. I decided that due to it failing so rapidly, a replacement was the best option. 

This was all agreed. Jumped through all the hoops of sending photographs etc etc. 

Estimated delivery date a week later. Not great but as it was a "we have to make it" option I grudgingly agreed. 

Sent me a tracking number. Tracking didn't update. At all. Friday comes around. No delivery. Contact the team I was talking to. "Premium" engineer assures me that it's out for delivery and that the servers are down and that's why I can't see it. I ask for tracking info for delivery company. He is evasive. I push him on this. He eventually says I need to speak to customer care and transfers me. They tell me that he had lied. That the order was on hold for an unknown reason and that they would make some enquiries by sometime the following week "48 working hours" whatever that means. I am by now utterly frustrated and angry and starting to feel like I should cancel the whole thing and say I want to discuss this, but they tell me nobody can talk to me about it as it's a Friday and I should just wait for the replacement as it will probably be with me by the beginning of the week. Get told a manager will call. manager does not call. Monday comes around and each department - "premium" technical support and customer support are blaming each other and nobody can tell me where on earth my replacement laptop is or why it has not even been built. I am getting very frustrated. I'm a disabled man and this was supposed to make my life easier. It has not. I've had the worst experience and I can't get a straight answer out of anybody and I don't know what to do. I've had dell in the past a few years ago so chose them when I made this investment as I liked their systems but I never expected to have such appalling customer care. I have a £1700 brick, no replacement and no updates. I have no idea what to do. Any ideas please all?