White background
 

Why do my white backgrounds come out a dull grey? I've tried different lighting techniques but nothing seems to solve the problem.

Any advise most welcome....

Regards

It's pretty simple really. The meter in your camera is set up to achieve an exposure giving a 50% neutral grey. If you shoot a plain white background on auto the end result will be pretty much the same as if you shoot a black background.
If you want your background to remain white (or close to it) you'll need to spot meter on something which is, tonally, 50% grey.
If you're shooting a model, don't meter the white background or her black hair. Go for a darker skin tone (shadow under the nose for example). Many pro's carry a 50% grey card with them and meter on that.

are you lighting the background up ?

you need to light the background as well as the subject to keep the background white