Formula for monthly spend on personal budget

Hi, I am working on my personal budget spreadsheet & really struggling to work out a certain formula I need. I'll explain the layout of the spreadsheet in the hope someone can help. I have an overview of the year (the red table pictured):

As you can see, I have different areas of spending on the left, e.g. groceries, clothes etc. I have headings for these such as 'General' & 'Business'. These might look a bit like Numbers 'Categories', but they aren't; they're just normal rows I made a slightly darker colour. As the picture shows, I have some 'header' columns that summarise the whole year. I then have columns for each month.

It's the monthly 'Actual' columns I'm having trouble with. I want to pull figures into this column from my transactions tables lower down, but I can't get it to work. As an example, G1 needs to be the sum of all my 'Groceries & toiletries' transactions in January of this year, from the various tables I have for my different accounts. Here's one of those transactions tables (with personal info blacked out.) This one is for my current account, others are for my credit card and a savings accounts.

In these tables I have categories switched on to group transactions by month. Column A is usually hidden. I only added it because I tried to find out how to do this before and it was suggested to add a month column to help the formula work, but that was on a simpler sample table with a different layout and I haven't been able to get that to work here.

I'm think I'm ok with how to get values from multiple transaction tables, I think I just need to use a plus sign & repeat the formula. The problem is I can't get the formula right for even just the first table.

Can anyone help please?