You see, I was going to suggest a Mondeo - after having the Astra written off I bought one and thats what I drive. Everything about it is better with the exception of:
- lack of air recirculation function on the heater
- quality of some of the interior fittings is low and flimsy
Other than that, even on a 280k mile old ex taxi, handling, brakes, comfort, space all better. Its been perfectly reliable over the last 11k miles I've had it (as was the Astra, to be fair) and believe it or not, my motorway commute to work returned more or less the same fuel economy (its a 1.8).
Sure, I had to pay a difference for the insurance (grp9 vs grp6) but if you're going for one of the higher power astras (the 1.4 SPI is dog slow as I mentioned, to the extent that it becomes tedious) you will be looking at a similar insurance group as a Mondeo.
Just do some quotes, and see what they return. You might want to try Norwich union as they seem very cheap for young drivers. Mondeos can be picked up for 2-300 pounds on auction sites and autotrader.