I'd use the Moneysavingexpert money makeover to get the best idea I could of how much the household spends in different categories and then separate the money out accordingly. You can move money around on payday into appropriate accounts, such as:
An account for all the fixed monthly costs like mortgage, council tax, utilities etc.
Savings for annual and irregular expenses like Christmas, insurance, holidays, broken cars, pets and household goods etc.
Long term/emergency savings for illness, redundancy etc
Day to day family spends - food, travel, days out, ad hoc family expenses. You may wish to separate these out between essential and discretionary - it's up to you.
We do all our spending on a credit card that is paid off every month from the joint account and earns cashback and I do a bit of 'behind the scenes' accounting to separate his/hers/joint expenses.
Finally, what's left is split 50/50 for adult personal spending, on a when it's gone, its' gone basis.
You might be able to download a year's worth of transactions from your current accounts and any credit cards, to try and work out the food, travel etc spending as it's often all categorised, although some of the categories are a bit weird, eg I think McDonalds comes up as 'entertainment'.