I keep having to top my brake fluid up??

there arent any puddles under the car??

does anyone know any tricks to find leaks or will it just be a case of checking EVERYTHING brake related?

look for sign's of pealing on paint, have you noticed any difference under heavy breaking??

possibly when you did the 5 lug you may have not tightened up the brakes lines and it just squirting in the arch and dust is drying it up!?

jack the car up and have a look round, proberly sumat stupid.

Yeah il have too

It brakes perfectly fine, but it good to know it could be better

It could be something stupid like a bleed nipple needs tightening. Id get a mate round, jack it up+wheels off, engine off and pump the breaks. Get your mate to check the lines at the calipers for any fluid.