had 2 bottles from the back brought up to cater for any cockpit smoke)
They wouldn't have helped if you had smoke in the cockpit, portable "constant flow" systems mix surrounding air with the oxy. as you breath in. The flight deck masks are "diluter demand" systems and do the same thing when they are in the normal position (unless you are very high) which is why they need to be set to 100% to protect you from smoke. Part of the de-press drill should be to set the flow to normal if there is no smoke.
In my opinion loss of flight crew oxygen means land at the nearest suitable airfield and range and terrain permitting descend to 10000ft.