is it possible for me to upgrade my main beam and fog light bulbs to hid bulbs without it affecting electrics

Anything is possible, why you want to is a different matter altogether.

Main beam HID bulbs are pretty pointless as they take a few seconds to warm up to give full (or even useful) light output, they will also fail pretty quickly as HID's don't like being tuned on and off frequently.

As for the fog lights, the light output be be such that they will be far too bright to be useful in fog.