Dangerous ground. You dig a small hole, and then a little a bigger, before you know it... your stuck.

If you have concerns, then that tells me you shouldn't be using it. My advice would be to create some generic examples based on things you have done for real. So take a brief and change the details, create something new in you spare time. Much safer.

Other option would be to get on a freelancing site, like Elance, and build up a small portfolio from there.

You really shouldn't be using examples you don't have the rights to. Assuming your previous employers aren't apes, then switching your names around isn't going to take a genius if they see it.

Good luck!

What exactly was wrong with the quality?

Usually you approve a proof? And the job was produced as you specified?

If you have let them produce something without seeing a proof, then you're kind of to blame in some respect. But most printers won't produce a job without approval either, so I'm struggling to understand where the problem has risen from.

Did you design it? Or did they?

I think it can and does, advertising influences thee world to buy. Whether it's print or digital media.

Love you example though, very funny.

I'm in exactly the same position. I've recently done a few jobs on the side and I'm not sure where I stand tax wise.

I had a look at the Tax website, but it's confused me more than anything.

The main thing I'm concerned about is that if I do have to declare, will my current employers find out?