Played all day long without a single crash to desktop. Here's what I did, not sure what was the fix.

Used the 4GB memory address tweak, applied it to the TESV.exe http://www.ntcore.com/4gb_patch.php (This is for people with 64 bit Windows)

Went into FFDShow audio settings > Directshow and added TESV.exe to the blocked list. Noticed there was already fallout3.exe by default in that list, so it may have been a known problem on the older games.

Changed audio to 16 bit , 44khz

Changed threaded optimisation to on in the nVidia control panel.

Disabled the background processes involving my kb+m (Roccat Kone+ & Roccat Arvo)

One of the above sorted the problem out.