Astra is your average FWD hatch, 1.8 should be fairly nippy.
But on the note of fuel and 'thirsty' Omega, there are a lot of people saying they are going to get rid for something better on fuel due to costs, but i don't get why people chop them in. :-/
Looking at auto trader:
http://www.autotrader.co.uk/classified/advert/201041370623597/sort/priceasc/usedcars/price-from/6000/model/astra/make/vauxhall/page/1/radius/1501/postcode/tw89de/quicksearch/true?logcode=p£6k gets you a basic spec Astra.
The most expensive 3.2 Elite Omegas around cost £3-4k - Lets say its worst case of £4k, that is still £2k cheaper than an 'Economical' FWD hatch.
When running the numbers for my LPG conversion, a £700 conversion cost, which saw a 30-40% saving in fuel cost, would still take approx 7,000 miles to re-cover my costs, assuming I saved 10p a mile, worst case it would take me 10,000 miles to recover.
So anyone spending just £2k more on a more economical car, is going to have to do roughly 20,000 miles before you break even, and thats best case!
V6 Omega does drink fair bit of fuel, but its cheap to buy, cheap to maintain. That counts for a lot, so don't get too hung up on mpg
