Financial Requirement (cash savings)

[Henderport]

I'm in the US and I am applying for a 6 month settlement visa to join my fiance in the UK.
My fiance is combining his savings with his income to satisfy the financial requirement. The minimum amount he will have in one account after 6 months is around 15,000 GBP (he's accrued more but it hasn't been held for 6 months). In a separate bank he has a 40 days notice savings account with 35,000 GBP. As I understand it this money does not satisfy the requirement because it cannot be withdrawn immediately without notice. Can the requirement be satisfied if he withdraws it and, deposits it into a savings account that doesn't require notice to withdraw from before we apply? Will it have to sit in the new account for 6 months or does the time requirement not matter since we can evidence he's held it for 6 months albeit not in account that's liquid? Does all of the money need to be in one account at the time of application or can you evidence a sum based on two separate accounts?