Last help, then I'm gone. I looked at that link from user Ivor Toolbox, seems to cover British Law mainly for people booking there
https://www.moneysavingexpert.com/ne...d-your-rights/
this section covers your case
I've a future trip booked – what are my rights?
And this would confirm what I worried about
: Even a voucher is optional, they are not obligated to.