I think the first piece of advice I would give, is double check the weather for tomorrow. I've just looked at MWIS and it is suggesting a cloudbase of 350 mtrs. Considering the plateau is well in excess of that, at around 600 mtrs, it might be wise to consider another day.
http://www.mwis.org.uk/mountain/PD.PDFIn answer to your question, the plateau is generally featureless with lots of water eroded ravines. That doesn't mean there are no features, just that they are very few and far between. So your navigation skills ideally need to be very good for a safe passage, even with the use of a GPS!
If the GPS should fail, then you would need to fall back on good nav skills, in low cloud and very likely rain and the strong possibilty of buffetting from the wind.
Though I've not walked the outer edge of the plateau, it does look like there is some form of navigable footpath,m but how good and hoow much, I do not know. Perhaps someone else might be able to advise on that one.
Unfortunately, I'm busy the following weekend, otherwise I would offer to join you, weather permitting.