The organisation you work for is skating on very thin ice. It is quite difficult (legally) to just pick one employee out of the air and make them redundant - and they certainly cannot replace the post within 3 months if they do declare a redundancy.
It really depends what deal they offer you. If you are in the market to be made a deal then it is possible for you to sign a 'compromise agreement' for which your company should ensure you receive independent legal advice at their expense where you essentially sign away your rights in exchange for a (large) dollop of cash.
If you wish to stay, the evidence that you have managed to obtain by accident indicates that your organisation is trying it on. Keep the email. keep cool, say nothing and see what happens. The way this is heading, you would have a reasonable case for unfair dismissal at an Employment Tribunal. Such cases typically result in cash settlements and/or the job back.