I use an old laundry table made with an angle iron frame and a wood top. It is approximately 4 ft by 18-20 inches deep. The table is standard table height.
But, my presses are mounted to free standing floor stands and not to the table. They are heighten than the table, approximately kitchen counter height, plus/minus. Apologies that my reloading room is not handy to my current location.
Frequently, I have to clear the table off to keep working room. That is good, keeps the junk from piling up. I have shelves and storage drawers to catch the equipment and tools that are not in use.
For the press height, make your mount so that it can be changed, height wise. Then, if you pick a height that is not comfortable, you can change it without too much difficulty. It is one bridge you do not want to burn until you figured out what you like. If you are not comfortable while reloading, reloading will be a chore.
i sit in a chair while reloading. many folks sit on a stool or stand while reloading.
Finally, build your leg system sturdy with no flex. I suggest good bracing, bolted or screwed connections with adhesive in the joints. The bench does not have to be heavy if you have accounted for the various forces applied to it by the press, but weight can make up for poor geometry and bracing. In either case, flex is not your friend.
Hope this helps. Have fun building your bench.
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It was built in place. I put shelves along the back and the effective depth is now 32" It does seem to collect a lot of stuff. It's just too big and heavy to take it apart and cut it down. 
