It's a great trip.
I fully agree with Hoehlenforschers advice. Take 2 ropes. Apart from guarding against getting the rope stuck, it also means you can rig both halves of the big pitch. The ledge half-way down is one of the most miserable places on earth! Doing the whole of the big pitch in one hang is not advisable, because (a) you will get wetter and (b) there is more chance of getting the rope stuck. A pair of 40-45m ropes is the ideal tackle.
Route finding is easy, provided you have the right cave (don't abseil into Turbary Pot by mistake!) After the water from Simpsons comes in there is one short cascade into Swnsto Great Aven. At this point go down through the boulders (to the left facing back up the pitch) and then follow the obvious passage on. If it gets very low and wet, you are going the wrong way. Once you can hear the rumble of the master cave, you can't get lost. Follow the stream to the sump and the pitch up.
There is often a dodgy bit of SRT rope on the pitch up into the roof tunnel (there was the other week anyway). Whether you trust this is up to you. If you climb the pitch, climb up the far side of the pitch (in the alcove away from the stream), followed by a bold step across to reach safety. I don't find this a particularly hard climb, the secret is to choose the right place to start climbing in the first place.
Above the pitch you follow the obvious passage most of the way. There is just one critical junction where you turn to the left (the passage to the right goes to Toyland and Carrot Passage).
Obviously this is not a trip to do in wet weather. If the cave floods, the best place to sit it out is Swinsto Great Aven. Alternatively you can find the start of the bolted traverse which takes you above the entire streamway. You can sit out a reasonable flood here or even make your way along the traverse to safety.
Mark