As someone trying to learn how to bat after a decade away from the game I've got the same problem. I can play down the ground and through the offside without too much trouble yet a half-volley on my pads is a dot ball.
Won't be able to work on it now that Ramadhan is approaching but in my own case I think there are two changes that I could try:
The Quick Fix: Open up my stance a tiny bit.
Pros: This will stop my pad getting in the way of balls I should be playing through mid-on and midwicket.
Cons: Doesn't necessarily make the leg glance any easier and if I open up the stance too much it carries the risk of messing up my ability to play the cover drive and square cut.
Getting my head to the ball: AKA learn how to bat
Pros: If your head goes to the pitch of the ball, your feet tend to follow. Centre of gravity and GCSE physics and whatnot. Improves your batting all round, how does it help with leg stump balls? Because getting your head forward makes it easier to play the ball without your pads getting in the way. See Exhibits A & B presented below:
See how, even though he hasn't made a big stride forward he's in a position where he can flick the ball to the legside pretty easily. That's because his bat is out in front of his pads. The danger here is that you might end up driving the ball in the air if you don't get your timing right.
Compare that to:
This gentleman above will be feeling pleased with himself because he's heard all the TV commentators so he's got a giant stride in. Unfortunately for him, he's not in a position to flick the ball to the legside because his pads are going to get in the way of his bat.
Cons: It's hard work to overhaul your technique like this and requires a friend who is generous and extremely patient to come to the nets with you and spend hours throwing the ball at your pads until you get it right.
Of course, as Pakistanis we are also able to adopt a third method to eliminate the ball hitting the pads:
Get your front foot out of the way and swing as hard as possible: