First, Pasta ... don't panic.
Here is some reading for you, if you can stand it...
https://www.lease-advice.org/advice-guide/section-20-consultation-private-landlords-resident-management-companies-agents/
You should have been informed at several stages. Before tenders were invited; during award of tenders; consultations to award tenders etc etc
Unless you've not been reading your mail, you should have received several communications.
It is beyond common sense to have something like this suddenly dumped on you.
Talk to your neighbours. They will be in the same boat.
Also, does your lease state that payment should be up front (before works begin)? This is extremely short notice.
It may well be that the Management Co. can authorise this work, but somehow, someone has gone about it the wrong way.
Do take legal advice. Invite contributions from other leaseholders, to cover cost of legal advice. The same advice applies to you all.