If you are not expecting those emails, then I would consider them to be phishing attempts.
As for this:
I do mine, pathetically with GUIMiner using my graphics card. But I was planning on buying a Raspberry Pi Motherboard and some Block Erupters. My machine is hardly ever turned off anyway.
I no I'm never going to get rich from it. I would like to hear your thoughts on this is it worth it or a complete waste of time?
Even if your computer is on all the time, you will pay more for the additional electricity used to mine than the bitcoins are worth. Same for RPi and Block Eruptors.
If you are doing it for fun, then go for it. If you are trying to make a profit, then you are wasting your time.