Ok bit of a weird question but if at all possible I had intended to use the ''city light'' wiring that's already in my ZX12 loom to power my side lights but I've since found the city light is only 5w. As it's the same circuit as fuel pump, injectors etc I don't want to kill it if I use a bulb that's way more than that (would that even happen?)

Side and tail lights are generally 5 watts.

cheers mate, so I guess an extra 5w bulb on there's not going to upset things too much, that being said I suppose it'll actually be an extra 15w with the rears too but that will be fine I'm sure.

Should be be 5 watt ---- don't put higher output bulbs in -- especially don't but higher wattage bulbs in the tail lamps the reason is the brake lamps should be instantly noticeably brighter than the tails.

If you use LED lamps you'll be well under 5 watts even with all four lamps.

+1 for LEDs - they can save you a LOT of power if things are tight. The only conventional bulbs on my car are the main beams (dips are HID) and I can power up all of the side lights and indicators on a torch battery!