I have over the years acquired several store cards. Most of these stay in my car. Come the winter they're great for scraping the ice off the windscreen.

As for the junk mail - take out and throw away anything that refers to you or your address. Wait until you get more junk mail with a return envelope. Put the first lot of junk mail into the envelope and post it.   
We're sure that lots of the banks want to hear about others "Super Deals" on loans, car insurance etc., so we'll just forward the details to them!!!