I just wasted most of a day trying to sort out the data import GUI and problems with sizers. It was quite frustrating, but I managed to get most of the problems sorted out finally. It is now connecting to various databases and showing a sample of data which users can browse and select what they want to import from.
Oh, and it imports the variables too which is good. It is so nice when problems eventually finish. I have lots more work to do tomorrow (csv importing - I wrote my own csv module to deal with little problems like missing data in the middle of a row) but I am also going to my wife's family's village for a fiesta. It's been raining all day, so here's hoping the weather improves. Here's a picture of the village in sunnier times.
Either way, the work is coming along really nicely now. The project is not yet 50% finished (my estimate), but it already imports data from databases, allows a range of operations on them, and can produce even complex descriptive analysis. It's looking good so far.