First of all:
Why are you depending on only one bank account to run your business? It's very easy to set up two or more business bank accounts and use them both. Just like you have back-ups for your data (right?), it makes a lot of sense to also have financial back-ups for your business.
Same with the debit/credit card - is that all you've got for business payments? Why don't you have more than one card? Why don't you move things over to a personal card while you open a second business card?
It's too late for that now as the author didn't set that all up ahead of time, but instead of complaining on the internet, why don't they start moving things ASAP. I've found Santander incredibly easy to get up and running with (same day almost), compared to Barclays...etc.
Look, you're running a business, and your job running a business is to keep it running. If you haven't thought ahead to such possible events, you're doing your business a disservice.
So my advice - call Santander, start switching things over, stop broadcasting things online, and focus on keeping your business running. You can always do a recap later once things have died down.
And I agree, HSBC are a complete PITA. It's far too much trouble even getting a personal account with them, so a business account would be far more effort than I would be looking for.
Even Barclays wanted an in-person meeting (even though I've banked with them for decades) to open a business bank account. And the only date they had available was a month in the future. Yup, I cancelled that appointment.
So, build redundancy into your business. At the very least a second bank account. It's easy, but as you can see, so very important. Just IMHO.