Banks reconciliations - difficult and lots of transactions!

Bank recs for 6 months. Quite difficult as there are 6 banks accounts that need to be treated as 1 bank account and 4 cash books that need to be treated as one cash book. One bank transaction can be made up of 3 different cash book items and vice versa. Can take up to a day to complete 1 month and I have 6 months that need doing as quickly as possible. All back up for paying in books and card receipts, and cheques/bacs payments will be provided.

Can't use a look up formula because of the format of transactions so this is a manual matching off!