wattage
 

Just had a new light fitting installed and didn't take into account how dull three 20watt halogen bulbs would be..can i replace the bulbs with a higher wattage? if so how high could i go? The light itself isn't on for long periods.

You need to check if the light fitting has a max wattage rating.
Also consider where the light fitting is instaled,
and whats behind it, ( ie - is it well ventilated ).
Check these things before you chamge lamps.