I just bought myself a UPS for just under £40, so no more failed prints due to power fluctuations (I had two in one day the other week ) and it will even survive a power outage although I don't know how long for.

If you're going to be doing long prints consuming large amounts of filament then buying one would be a wise investment, not too mention saving on the frustration as well

@ Joao - It says 500VA 300 watts on the UPS unit. Do you have an idea as to what power my printer may be using (210 extruder & 95 bed) and may be how long it could survive on the battery back-up?