We have the following helpful guidance drafted in respect of furlough and redundancy which is helpful in your position.
Can my old employer re-hire me and put me on furlough?
Yes, the furlough scheme specifically allows this if you were on the payroll and stopped working for them after 19 March 2020. You should speak to your ex-employer and ask whether they would be willing to put you back on the payroll and designate you as ‘furloughed’. Your employer may very well agree (particularly if the business is likely to recover quickly after the crisis) but there is no obligation to do so.
It appears this is what your employer has done
Do I have to re-pay any termination payments if I am rehired?
You may have already received a redundancy payment, notice pay and other lump sum payments. It is entirely a matter of agreement between you and your ex-employer on whether you would have to repay any sums already received.
It would appear your employer has made you redundant however it is not clear whether they have followed the correct consultation periods etc.
what is your ideal outcome in the scenario. Do you wish to rejoin the company or sue them for unfair dismissal?