Your SQL is looking for a DATE to match a DATE in the field "Week_Commencing". That suggests a couple of possibilities.
One, are the values in question actually DATES, or strings FORMATTED to look like dates. To the human eye, of course, they could appear to be the same, but to Access the Date DataType is different from the string datatype.
Two, your SQL uses the string delimiter, which is the apostrophe ' but you are trying to work with dates. so you'd want to use the date delimiter # instead.