Tim suggested I bring the old bike in and they would quote on fixing it. Then I could decide whether to do that or buy a new one. He said that by the sounds of it (new tyres, new saddle, look at the gears and the brakes) it would not be anything below $200. Heard that joke about the farmer's axe that has had 10 new heads and 5 new handles?
He showed me three bikes: a Giant (American) for $585 that had big tyres, ergonomic handles and turnoffable suspension; an Avanti (NZ) for $585 that had wide tyres and fixed suspension; and, another Avanti for $399 that had thin tyres and no suspension. The saddles were all the types with the holes (yay!). He did not go much into brakes and gears except to say they were similar to all three and that the main thing for me would be comfort.