Oak on concrete flooring

Hi folks,
My living room floor (15m2) is about 120 years old. It is pine, nailed directly (no battens) to a concrete floor which has NO DPM. The iron nails have rusted and this has eaten into the surrounding timber causing holes.
My original intention was to replace it myself, using oak. However, the more I investigate this, the more complex it seems to become. The old concrete is not smooth and so I presume I must apply a screed to level it. Then apply a liquid DPM (something like Ruberoid Synthaprufe?) and then use a flexible adhesive to fix the floor. The original boards have been sanded at some time in the past, they are now 21mm deep but guess that originally they were 1" boards. Then I am advised to use an underlay (circa 2.5mm thick) which is going to reduce the thickness available for the boards. Someone even suggested the best route would be to tear up the old boards, dig out the old concrete and replace with a new, dpm'd concrete base.
I need some sound advice or I am just going to leave the whole thing until my daughter inherits my house!!!
Anything you can suggest will be most gratefully received.

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