Sometimes, if you are heavily infested, you need to get serious!

Now here's a site with all the pesticides and sprays to kill off a complete army of spiders in your house.
Please always read the details carefully, to avoid causing damage to any other living things (including yourselves!).

It's all a bit technical for me, but they sell a spider elimination kit here for $69 which will be enough for most infestations and all you need is a garden sprayer which I believe they sell on the site too.
Again, USA only and even then, they only ship to certain states so please check before ordering.

Click here for the website