Offer your thoughts or opinion on the input financial query or topic using your financial background.

eBay Account and SIM cards sent to my address
In your mother's position, I would do two things: Get a copy of her credit report. Money Advice Service has a useful page on how to do this - it is cheap (£2) or free to do and will immediately tell you if someone else is using her address for anything untoward. Check with the Post Office whether anyone has set up a redirect on mail to your Mum's address. You can redirect by individual names, so if Joe Bloggs buys a bunch of stuff and has it sent to him at your Mum's address, he could set up a redirect at the Post Office so any post for Joe Bloggs at that address gets redirected to Joe Blogg's real address. There is a page about this on the Post Office website, I don't know exactly how to check if someone else has set this up but I'm sure the Post Office would help you find out. Additionally, I would consider visiting the address (the same house number in the "Road" where hers is in the "Avenue") and see whether the occupants have anything useful to say about this. I would just say you'd had some mis-delivered post, and want to check what their names are so that you can pass on anything that is intended for them that comes to your address (and ask them to do likewise for you). Depending on how that goes you could also ask about the ebay store and see whether it really is them that set it up.