Reading your posts you remind me of how I was 10yrs ago and we did our DS in Gib.
You do need to worry a bit more about navigating around Gib as with good weather you should manage an amounyt of Spain and N Africa possibly Ceuta.
Enjoy your DS - you seem to have the right attitude to do well.
Where will I find this computation graph for tidal streams as I have obviously forgot it and never used it!! On a X channel I look at the spring and neap currents, look at the tidal range for both and guestimate what it will be for the tidal range of the day I am sailing. Bigger the tidal range the more water has to rush in and out or am I being to simplistic?