Actually I know someone who is 19 and has a 2.5 CDX. £850 is not as scary as I thought it would be for him.
lawman (I remember you), welcome to the site. Omega owner or you not, you are equally welcome mate.
The Corsa, its image aside, is a good small car and a wise choice. When time comes to sell, you will have no problems, especially at that spec level. Just avoid tacky add ons!
And if you have any problems, let us know and we will try to help.
I am 22, got the Omega at 21. Facelift 2.2 CD - £450 Fully Comp 4 Years NCB (Its about £500 with the legal protection)
I find the Omega is fantastic, extremely smooth and refined. Yet quick (ish) when i want it to be.
From what I learnt on here, 2.0 / 2.2's are good, not lightning fast but no slouch either. They are also easier to maintain.
Get a V6 if you want pace, mpg is lower but only slightly. - A V6 would be steep on the insurance, maybe get a 2.0 for a while to get some NCB's and then go for a V6.
Just finishing off upgrading the ICE in mine, adding a new Headunit & Active sub. I am no hooligan either just wanted a little more bass in the cabin and mp3 playback