"Best before" is a somewhat arbitrary date given to foods that will not cause you too much harm if they begin to decay. Sultanas will grow mould on them when they deteriorate and that is unlikely to happen just a month after the "best before" date.
Retailers are gradually getting rid of the terms 'Best before date' and 'Use by dates'. Co-op has already stopped putting it on most of their products. Lets face it years ago they didn't have dates on them. Tinned products last years and you knew whether or not to use them as the tops and bottoms would blow outwards.
Best before and use by dates are a supermarket con to make people buy more food. Also to waste more.
My nose and eyes tell me if things are fit to eat.
They will be fine especially as they are unopened.
Some of the stuff in my bakery cupboard can be there from Christmas, opened but unused, until the next Christmas or even the one after that.
It all gets used eventually and we’re still alive ;)