So I got it out! but the reason it was stuck was quite unfortunate. It looks like that the flood was so bad that the unwanted plastic collected above the heating element and prevented the spring release mechanism from working. If the wires to the heat element were still connected, it might have been possible to melt away some of this plastic.
My advice if you suspect this has happened to you is to accept that your print core is busted and remove sections of it with pliers being careful not to damage the rest of the printer. Then buy a replacement core.
In most other circumstances the heat gun approach would work, but in this case it risked melting other parts of the printer which would end up costing you more than just a new print core.