Your first paragraph is correct when the company runs out of money but the Administrators have enough to pay wages, the rest coming from the Government's fund.
Your second paragraph sounds dodgy in that the Administrators can't just choose not to pay salary to redundant employees - they obviously have no money. Such employees are preferential creditors and generally do get paid (late) when the company is broken up or sold.
So the same situation applies to you - and the Administrators are presumably hoping that enough money will come in to pay salaries by December end (the reduandant employees are due money now because their contracts are terminated).
You have your terminology a bit mixed up, because Constructive Dismissal is when you resign because the employer has behaved so abysmally that you claim the contract is broken by them. I suggest you do not resign under such circumstances because I suspect that THEY have to dismiss YOU (on grounds of redundancy) for you to get redundancy money (either from the employer or the Government fund.
A bit of a bummer - I can't see a way around it.
You will get the money - but I appreciate that it's the timing that's the issue.