For the 2km: Start at the bins and head up the tan towards Government House.  Turn around at Govt House Drive and head back to the Pillars. The 750m reps are run out and back along the bottom of tan. Recoveries are 4 mins/2 mins SR.  
Alternate session: Reduce (or increase) the number of 750s.

Use the 250m markers along bottom of the tan. So the full session is up to the 750m marker and back twice, plus up to the 500m marker and back once.
Suggested recovery is 'on 1.30' but could be cut to 'on 1.20'.
For a speed session cut the number of reps to 10-12.

The session starts at the 400m finish (near the café), and is two laps of AOP, with the finish approx. 14m short of the start line.  Suggested recovery is 'on 5.15'.

This session is 5 sets of out-and-back reps. Start each set (i.e. odd rep) at the Pillars. 
1) Run for 2 mins clockwise, wait for 60 secs, return. Re-group at the Pillars. 2) Run for 5 mins anti-clockwise, wait for 60 secs then return. 3) Run for 1 min clockwise, wait for 1 min, return. Repeat. Recoveries are all 1 min stat rec. 
 Options: (a) skip a set or two to reduce total volume.  (b) increase the 1 min reps to 75 secs (and take only 45 secs rec) to reduce intensity.

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Start at Pillars and head up the tan towards Government House. Turn around at Govt House Drive and head back to the Pillars. Once reaching the Pillars turn around and head back, completing four laps. Start steady and increase the pace for each 2km section.
Alternate session: reduce to three stages/6km (skip first or last stage)

Run from the Pillars to the 750m mark, then 500m back towards the Pillars and then 250m to return.The tempo of each set picks up as the distance of the rep decreases. Complete three sets in total.  
Recovery: start on 4.30, 7.45 and 11.00.
[Alternative session: skip the last set or scale it back e.g. finish with 2 x 500m or 2 x 250m.]