Keeping a large amount from house sale safe?

Hi all,

My mother has sold her house and the house she is buying is in the process of being built, so as such the money for her house sale will be in the bank for a few months while she stays with us.

We are quite savvy with cyber security and whatnot, but because it is such a large amount of money we obviously want to be particularly careful.

She has two bank accounts so first things first we were going to split the money between them, then also thought about maybe putting some in my bank account and some in my sisters (The amounts would all be under the 85k needed for the FSPC, though I understand they cover for more in house sale situations).

Then I thought about transferring the amounts into at least a saver account linked to the bank, rather than the current account itself, so there is an extra hoop for a proverbial hacker to jump through.

We'll have 2 step authentication and spending alerts on each account.

Does anybody know of any ways we can get a bank to essentially 'freeze' an amount of money so that it would be impossible to spend it in a certain time period? Or setting a limit on how much can be spent or transferred in one go? I will be asking this at the relevant banks, but so far haven't seen much info on it.

Basically with such a large amount of money in the bank I am looking for as many ways as I can to make it very hard to spend/transfer the money in the months leading up to the purchase. Can anyone recommend anything beyond what I am doing?

(Btw its scammers I am fearing with regards to these measures, not my mother's spending habits)