Air crashing and will not reboot

I've been using my 2010 Air in Tobago for the last day or so but it's now started to have problems and will not reboot.

Initially it seemed slow to restart from sleep mode and then it required a full reboot from sleep.

It was then fine for a few hours but suddenly crashed and took a while to reboot. It then crashed again and refused to reboot at all.

I left it overnight and it booted up first attempt this morning but then crashed on log in. It now appears to have no life whatsoever. I've tried resetting SMC but this did not work.

Applications running have been Mail, Firefox and Chrome.

Voltage here is a little patchy and I wonder if it could be a power issue? We've had some power drops and, presumably, surges when the power kicks back in. These are not enough to turn lights off but they have caused my JBL iPod dock to cut output and require an off/on restart.

The Air had about 20% or less power at the time of the last crash yet when I plug in the charger it lights green permanently rather an amber.

Charging of iPhones seems to be fine here and my wife's iPad is ok, albeit quite slow to recharge.

I'd been planning to do some work whilst out here and really need the Air to work with large spreadsheets so would appreciate any advice or guidance on bringing it back to life!