The lower the offset, the further out they will sit. Your standard wheels are ET52.5, a wheel that's the same width and an offset of say 42 for example, will sit 10.5mm further out than the originals.

If you buy a wider wheel you also need to take this in to account, if your originals have a width of 8J (8"), and your new ones are 9J, add an extra half inch in to your calculation.

Don't go for a wheel of too low an offset as it will mess with the geometry of the car and will wear wheel bearings quicker. Lowest I would go to not noticeably affect handling would be 42.