What really bothers me about this sort of thing, is the lack of FSCS protection. For any account that I want to use for more than a few bucks (and they encourage you to leave your savings in there!) this (or appropriate deposit protection in another EEA state) is an absolute must. (That’s why I keep no significant sums of money in my Revolut or PayPal accounts despite using both regularly - everything gets siphoned off almost immediately.)
Additionally, leaving FSCS protection aside, I would never leave any savings in a non-interest account. You can still get between 3-5% on your savings quite easily, which is better than nothing, and actually adds up quickly. (Although [just a little tip here] accounts that give cashback in some way or other can be more attractive for those not having several thousand pounds worth of savings.)
I do this sort of stuff semi-manually:
I use Wave accounting for categorising and keeping track of ALL our spending across our various current accounts and credit cards (between the two of us, there are now 12 accounts in total, so it would be a nightmare to keep these in order without a centralised record). You can connect your existing accounts, and then they’ll automatically import transactions, or you import CSVs if you don’t trust them (as I do).
I have a separate spreadsheet for budgeting, and once a month I sit down for a few minutes to reconcile it all, see how we performed relative to the budget, and make the appropriate transfers as needed. (Some accounts have minimum pay-ins, others have Direct Debits going out of them, etc.)
It helps that my wife is extremely disciplined and loves planning, but it still required between 10-30 minutes each month to ensure it’s all up to date.
If you have the discipline, it’s definitely doable, although the first few months will be tough, until you get into the rhythm.
Just my two cents, though…