I've got the Vango Icarus 500 too, and have just returned from a weekend of torrential showers. It's a brilliant tent, I love it!
Last year, Vango did a similar awning, but without the "front" iyswim, so it was more of a wind tunnel than an extension to the tent. I cooked very near to the front so that I was sheltered, but the stove was outside.
However, when the new one came out this year I bought it as the only thing missing for me last year was being able to secure it, and the 2010 version didn't have a groundsheet (although I did subsequently buy one and cobbled it together....)
Although desperate times called for desperate measures on Friday night and I did cook the evening meal in the enclosed awning.
So if you could get your hands on a 2010 one that might solve your problem.
Just to echo what Notwaving said. We bought the Icarus 600 last year with the open canopy and it's great. Loads of sheltered space, although we still cook well away from it. I didn't realise they now do an enclosed one! Although when camping with friends who have an enclosed one for their Tigris, we found we all set in our open canopy even when it rained.