My height-advice is:

"Looking straight against the side of the tyre you'll need appr.  1-2cm (a finger) space between the upside of the tyre and the bottom side of the plastic wheel arch. Doing so will preserve the comfort and also creates the look you want.

!!! L+R means you'll have to do something on the Left and Right side of the car !!!

Start putting the car on a level, straight surface (like in a garage).

Remove the spare tyre and the bracket where it's lying in ( watch the little (white) plastic clip not to jump away !).

1. Measure the height from the ground till the boot in a straight line. You'll have to do this L+R, on the same spot, write the figures down.
2. Put the car in 1st gear and loosen the bolts on the rear rims.
3. Jack up the rear end of the car (under the rear axle) and put the car on 2 stuts from the same height.
4. Remove the rear rims.
5. Remove L(1)+R(1) the bolt from the handbrake+ anchorrplate (13mm)
6. Remove the bottom bolt from the right shock absorber (17mm), absorber should be hanging loose now !
7. Remove the (13mm) secure nut+ring at the rear side of each torsion bar L+R, watch the end NOT to turn with the removal of the nut!
8. Remove the secure plate from the torsion bar (plastic torx bolt cap, and a torx bolt with a a-symmetrical ring ). Before doing so de-rust everything well !

Watch it !: if the bolt doesn't loosen immediately you'd better use a little sharp pointed hammer-tool to loosen the bolt. Doing so will damage the bolt minimally and you'll be able to use it again in the future !)

9. Now try to remove the front torsion bar out of it's housing.

Peugeot has a special tool for this job. It's a bar with a weight attached... you'll screw the bar in the torsion bar and using the weight you can remove the torsion bar out of it's housing. I used a home-made pulling tool which contains a big size socket (26mm), a M8x50mm bolt and something like 10 large size washers to fill up the space between bolt and socket.

Now put the socket over the screw hole of the torsion bar and screw the bolt into the torsion bar. Gently screw the bolt in and try to pull the torsion bar out of it's housing doing so. The job might go easier when jacking up the suspension arm a little bit. Always be careful with the  end of the torsion bars since these fit very precise, and a little flaw (damage) will cause them not to fit anymore.

9. So the torsion bar is now loosened and lying loose in it;s housing: do not remove the bar completely ! The suspension arm will now fall down and on the left side of the car the security plate from the torsion bar will be freed.

10. Remove the secure plate from the left torsion bar (plastic torx bolt cap, and a torx bolt with a a-symmetrical ring ). Before doing so de-rust everything well !  (see point 7)
11. Push the suspension arm down and let it get back in place by itself.Measure the distance from the bottom of the brake disc (or brake brake drum) and write down this figure.
12. Now put a jack under the left disc (or brake drum) just to release the pressure on the torsion bar (like 1cm or so)
13. Remove the left torsion bar out of it's housing like you did before.... can be a pain in the ass with everything rusted..
14. Put the left suspension arm on the desired height with the jack (like 2-3-4 cm higher as the figured measurement : lowering the car = jack should go UP !).

Pay attention that the measurement in point 11 and 17 is not 100% the result in the end. The suspension arm will fall 1 or 2 cm down by removing the jack... so the best thing to do is after a try to lower the arm, release it from the jack and measure it again Push the suspension arm down and let it get back in place by itself. 

15. Push the torsion bar back into it's housing (watch both sides !!) by turning the bar until it slides easily into the housings.
16. Mount the ring, torxbolt and protection bolt from the left torsion bar.
17. Measure again the distance as described in point 11. The difference will be the difference in ride height (when not the same re-do points 14 and 15)
18. Punt the jack with the same height as eventually at the Left under the right suspension arm
19. Mount the torsion bar... also turn the bar until it slide easily into it's housing

Just to save some work and to be sure you'll get a good result (same ride height at both the left and the right side) you can now put the car back on it's wheels. Again, measure both the Left and Right side... and if there's any difference I'd do the right side again (from point 17). Or, if you don't like the result (to high or too low) you'd better start from point 8 again. Everything okay ?? >> put the car back on blocks and:

20. Put the jack under the suspension arm so the torsion bar can easily move into it's housing,
21. Mount the ring, torx bolt and protection bolt Right
22. Turn out the bolt ends (copper) from the torsion bar both L+R so the bar is put under some tension into it's housing... don't over-do this job, because the bolt-ends are not very strong ! Here you also can put the jack under the suspension arm,
23. Mount the anti-vibration ring and nut from the bolt ends L+R (don't let the end turn with fastening the nut !)
24. Mount the right shock absorber
25. Mount both the handbrake L+R bolt: if the bolt don't fit you can try to jack up the other sides suspension arm to free the hole
26. Mount the wheels and remove the blocks

Now you can measure again and compare the figures with the ones at the start.

If it all went like it was supposed to the height on the Left & Right of the car is pretty much the same.... and your Pug a little closer to the street..

Good luck !

Ps: Thanks Gareth, for checking and correcting some of the worst English mistakes... really appreciate it !