The first step was to clean up this bad boi, order a power supply and figure out what was wrong with it. It seems that it may have been an issue with the dock which is as of yet not fixed because I have been lazy and plugged the charger directly into the Roomba.
After a long charge cycle the Roomba fired up and started vacuuming up all the dust in its new home. Looks like one persons trash is another's treasure!
The next step was to dig up my Raspberry Pi and see if it still worked. Damn it the memory card was corrupt, just needed to reformat it. I went with Rapsbian (because I am lazy) using the installer on the Pi website: https://downloads.raspberrypi.org/imager/
Once the image was installed on the pi I fired it up and it worked like a dream.
Next step get the WiFi working so I can remote into the Pi from any device on my network. The WiFi dongle that I chose claimed to be plug and play ready for the Pi, and it was. No messing about with drivers, win! With the WiFi working I enabled ssh using the official documentation: https://www.raspberrypi.org/documentation/remote-access/ssh/README.md. Now with this setup I can simply ssh into the pi using the command prompt i.e. ssh pi@(the ip address)
Once the ssh was setup I configured the Pi so that I could use windows Remote Desktop Connection to access the Pi's GUI. TO do this I followed the steps on: https://pimylifeup.com/raspberry-pi-remote-desktop/
Now the Pi is all setup the next step is to get the serial going!