Done. Here's some pics - those heel blocks after fine sanding and polishing, plus mounted to the pedal. Those few mm in height difference make a noticeable difference - not huge but it's more to my taste now.
On the very last pic you can see that the 'U' end of one of the heel blocks is actually suspended from the ground plate - I have no idea how that happened. I simply assumed that the block would line up perfectly but it seems when I reworked the block I did so asymmetrically. Looks weird but there's no stability issues. I just never checked the blocks with the ground plate during the reworking and this is what turned out ;-)
On the previous pics the sides of the heel blocks had too much of an angle - which I noticed afterwards so I adjusted this and made them more lining up with the ground plate. I also rounded off the front contour, I thought that would look nicer.
You might notice that on one pedal I'm using different screws. When I got the pedals there were 2 screws missing. Funnily, I found one matching screw in our garage (why not 2? damn). We have a couple screws with the same threads but different heads. So I'll either get some more orig. Axis screws, use a mixed set or will buy a bunch of identical screws with matching heads.