Leaving Cowley around 08:00 we came up behind a full size dumb barge laden with a heap of scrap metal being worked up through Cowley Lock. We joined the tug in the lock. The boatman was repairing to the lockside cafe so would not impede further progress. He was concerned, however, about the gravel barges because his large vessel was blocking the lock approach. We passed ARUNDEL (without its butty) loaded with gravel in the next pound and were hoping that Uxbridge Lock gates would be open for us as we would expect. They were and we arrived just in time to enter the lock before the boatman operating the large gravel barge was able to turn it around. At the next lock, Denham Deep, a group of total novices on the Denham Boat Services day boat "Lovely Job" were receiving instruction and I think we caused a bit of confusion by leaping all around the lock as we do. Passage was, of necessity, a little slower than usual! Finally we returned to our mooring in the marina to find the car with a totally flat battery. It seems that the solar charger which I attach to the battery when away was no longer working. Charging up a totally flat car battery takes ages and after two hours there was still not enough charge to turn the engine over. We had to wait for another two hours for the rescue service to attend.