Shift Pattern Help

[Slaine]

Hi all,
I am attempting my first Excel sheet to try and make the yearly shift pattern a little easier to create/use as it's currently a complete manual operation.
I have attached what I have done so far but would just like some input/guidance on how to achieve what I need.
We have 4 shifts which repeat every 8 weeks and unlike most although there is a pattern of sorts it's not a standard one that I have ever come across anyway.

Within the workbook I have 2 sheets, the first, Yearly, is what I am trying to populate with the corresponding colors of the shift that they will work, January is already filled in manually and is correct as to how the pattern should look.

I just need each day of the week populated with either A,B,C or D in the correct order based on the pattern within the sheet, Shifts.

I think i need a combination of VLOOKUP,INDEX and IF formulas but this is where I am now at a loss and am asking for any help anyone can give.

Thanks in advanced