I got round to finishing my latest game (England, Standard Continents Plus, Standard size and time, King). I lost! See above for the details. As stated I was trying out different SPs to usual, had a decent tall empire, and was aiming for my first diplomatic victory.
SPs:
1. Liberty
2. Piety
3. Patronage
4. Freedom
Aside from Liberty, I don't usually go down that route. The three other policies useful but I'm not sure whether I should have swapped Piety for Rationalism to achieve my desired victory as Russia (runaway civ) won a science victory by some margin - around 15 turns. I also believe that Patronage was a waste.
I think though that the fatal error I made was a strategic one and I could still have won it using Piety and Patronage. I simply left Russia doing its own thing too long and by the time they started the space race it was all over in a few turns (their production must have been insane). I was safe on my own continent and had no worries from the other (two) remaining civs - even Japan! - and had some really good
peaceful tall cities.
I actually enjoyed using the alternative SPs and having a tall empire but on most of my games I play wide with Commerce and Big Ben I am able to purchase numerous units and launch an attack fairly quickly. Without Commerce and a tall empire I wasn't able to get to Russia in time.
Conclusion...
I am going to try out Emperor with a few more civs and again aim for a Diplomatic victory. This time, however, I am going to adopt a more warlike approach and take the runaway AIs capitals ASAP so that they cannot pip me to the post. I think I'll adopt a semi-wide empire with cities between 10 and 25 pop by the end game.
SPs:
1. Liberty
2. Piety (I'm going to give it another shot as I think I will need the happiness boost more than the Science boost from Rationalism)
3. Commerce (to finance my warmongering and to pay those expensive city states)
4. Anything or cherry-pick from the other trees
EDIT: I am still going to aim for those wonders too. Maybe when I move up to Immortal I will be cured.

And maybe I will take Rationalism. I'm not sure...