The carrot and stick approach shows that they know they can't force the changes on you. So you sort of have two options; take the new terms or don't.
The restriction on working in the same industry is brilliant and works in your favour. As TJ says, these covenants are typically unenforceable under EU law. But, the more ambiguous they are the more likely they are to be enforceable, so this one, with a very specific and punitive clause, is going to even more unenforceable.
The three months notice period works in your favour; yes you have to give three months notice but this isn't going to make any difference to your ability to find a new role. It does mean that they have to give you three months notice in the event of redundancy or such.
So really your only issue is the sick pay, which is a little scary and mean, but it's no worse than a lot of other companies and bear in mind that this is likely to be 10 consecutive days not cumulative.
The whole union thing is up to you; depends on where you stand on that debate really, which is not for this thread.