Stronglifts...use smith machine or not? HIIT after?

Oh, one other thing. You didn't mention how many sets you're currently doing. You'll want to get between 1 and 5 minutes of rest between your work sets (the more challenging it was to complete, the more you rest). Edit: Nevermind, you said 5x5 in a later post, so you probably already know this.

You'll also want to start adding in warmup sets once the weight is high enough (you could do this for your squats right now). Here's what I do for my warmups (using workout B as an example):

Squats (and everything except deadlifts, same warm-up structure)
10 reps with an empty bar
3 reps with 95lbs (pair of 25lb plates)
3 reps with 135lbs (replace 25lb plates with 45lb plates)
3 reps with 185lbs (add the 25lb plates back on)

... etc until I reach my work weight, then do the 5x5. I don't rest at all between warmup sets.

Deadlifts:
5 reps with 135lbs (pair of 45lb plates to set the proper bar height)
5 reps with 185lbs (add the 25s)
5 reps with 225 (replace 25s with 45s)

... etc. I'm pretty sure I read these warmup ideas (including doing full sets of deadlifts instead of 3 reps) from the StrongLifts PDF somewhere, but I don't remember for sure.

Edit again: You don't have to use the 25s-45s increments for your warmups, that's just what works for me to get a reasonable warm-up in and still reach my work weight quickly. Pick any steps that you want.

I don't use machines.. and I do HIIT after.. about 20 minutes.

I use the Smith for squats if I cannot get on the normal squat rack. I just add more weight when using the Smith.

No Smith.

If I do it HIIT it's on a non-lifting day.

I just noticed yo only do 1 set for deadlifts...5 reps!

Correct. I guess 5x5 deadlifts when you're already doing 5x5 squats the same day is pretty brutal. Never tried it; the 1 set is hard enough as it is.

5x5 deadlifts is pretty much impossible once you put serious weight on the bar - and it doesn't take long since this one goes up 10lbs a set.

I'm defor going to whack my weight up on deadlifts as I currently do 5x5 on deadlifts on my leg days at the moment. Instead of doing 40kg I'll try aim higher than this if it's just one set of 5.

You'll be adding 10lbs (About 5kg) every workout on deadlifts when you do SL5x5. Don't get ahead of yourself though. Just stick to the program. Deadlifts are a huge 'core check' exercise.

What you're doing out of the gym is just as important. Make sure you're eating enough food (at a calorie surplus would be best; based on your profile photo, it doesn't look like you need to focus on cutting any more fat right this minute), and sleep as well.