|Since we can't see your spreadsheet from where we're sitting, it's hard to say exactly what is wrong, but I'll take a guess...|
First, the date you used in Response #3 doesn't make sense: Mon 14/1/2014
If that date is supposed to be Monday, January 14, 2104, it is wrong. January 14, 2014 was a Tuesday. So let's assume you meant Mon 13/1/2014.
That said, if you are getting a #VALUE error when you try to add 1 to your "date" my guess is that the cell is not formatted as a Date and probably contains Text.
Here is what I did and it works just fine...
In F1 I entered this formula:
I formatted the cell as Custom ddd d/m/yyyy
Mon 31/3/2014 since that is the Monday of the current week.
In H1 I entered =F1+1 and formatted it with the same Custom format. The formula returned Tue 1/4/2014.
I then selected H1:I1 and dragged it over to S1. This produced the dates for the rest of the current week, formatted as ddd d/m/yyyy
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