Earthing problem

I have done a quick search on the forum and I cant find anything quite the same. First of all its a Squire strat I'm using. I have a hum that eases when I touch the strings, checking other posts it points to earthing problems.

Generally, hum that goes away when you touch the strings is noise. You touching the strings grounds you and lets the noise you have be drained to ground.

http://www.guitarnuts.com/technical/noisebucket.php

The humming is alot less if the volume on the guitar is at maximum and this applies even if I'm not touching the strings. I've had a quick look and all the wires appear ok. The tone knobs make no difference to the hum, the hum does vary depending on how the pick up switch is set.

That's to be expected since in some switch positions the pickups are probably in a humbucking mode. The noise probably decreases in positions 4 and 2 when you have the neck and middle or the middle and bridge pickups selected.
The higher the gain or drive is set the worse the hum is.

Also to be expected since the amp is making the entire signal including hum that is there louder.

Thanks, thats a really good website. I think I probally thought its a case of cheap single coils guitar, but I'm still left wondering if the noise level reducing(it doesnt go away but its alot better) when the guitar volume is at maximum points to another problem as well.