One thing to try, open Device Manager --> Network Adapters --> double click the Wireless adapter --> Power Management tab and untick Allow the computer to turn off the device to save power
Biggles 78 - couldn't find Device Manager access on Windows 8, but in Networking info. found a command to always connect to the Wireless Transceiver when in range, which was already ticked.
My failure to connect is very occasional and usually only when I run on battery and not mains power - my IT man says that is impossible, that there us no practical difference, which I would agree with, but that is my experience ! I usually solve it by shutting down completely and re-connecting the 240 V. supply, then re-booting.
Unfortunately we do get power failures, the last one shut down most of the Northern part of the North Island, and Vodaphone then discovered that their back-up cell tower batteries didn't work either !