Inspiron 15 7559 stuck in PXE Boot

So I have managed to get myself into a bit of mess. I was trying to sort out a separate boot issue with a new SSD I have installed to go with the HDD. I selected Legacy Boot in the Bios to see if that would help this issue and I now seem to be stuck in a PXE boot which obviously isn't working as there is no Network Adapter for it to get the boot info from. I have tried multiple times to access the BIOS when starting the laptop but I just cant get the BIOS to come up before it comes up with the failed PXE Boot screen. I do have an external HDD with Windows 10 on it but when I plug that in and try to boot to from that it doesn't work. In an attempt to get a system message to appear on screen so that I can get to the BIOS settings I have tried the following: - Removing a stick of RAM - Removed the HDD and SSD None of these have worked and it just goes to the same failed PXE boot screen each time. My next step is to leave the laptop running to run down the battery and see if a system message will come up but apart from that I am out of ideas other than taking it into a repair shop or contacting DELL support directly. I am obviously not an expert so if anyone has any ideas or tips, it would be appreciated!