Ancestry to ILR with 343 days absent!

Hi all!

Many thanks for your help in advance.

I am up for ILR in September 2014 with 343 days absent from the UK.

My Ancestry visa started on 26/09/2009.
I entered the UK on 8/10/2009 (12 days later) and stupidly activated my ancestry visa, even though I was only there for a holiday and left 10 days later on 18/10/2009. This is because I am a doofus.
I finally entered the UK properly to start work on 7/5/2010; (201 days later). I was meant to arrive on 17/4/10 but was delayed by the Iceland volcano (remember that!!) by three weeks; even still, that was 181 days after I was in the UK last.
In the 3.5 years since then I have worked continuously in the UK with the same employer. By the time I apply I will have four years worth of P60s, bills, tenancy agreements, etc. My only other absences have been annual leave, totalling around 140 days.

I am aware I am eligible for a few concessions under the new rules introduced late 2012. I know for example with the 90-day concession rule I can subtract the 12 days between when the visa was issued to start and when I actually first entered the UK and I could claim the three weeks delay for the volcano in May 2010. This would reduce my first year absences down to 192 days (including a holiday home I took in Sep 2010). If I got some supporting documentation I could even argue my return to Australia from Oct 09 to May 10 was for compelling reasons as I had a very ill grandfather during this time who finally passed away a short while later. However I would prefer not to use my grandfather as a reason as morally I'm not sure I feel comfortable with this.

I am also aware that the new rules introduced in late 2012 mean I can potentially be absent up to 180 days out of each year for compelling reasons. So it seems I am a borderline case; potentially up to the discretion of the individual case worker.

As far as I can see it, I have two options:
1. Take the risk and apply for ILR in September 2014. If I am denied, I will lose £1400 (or however much the same day service is these days); OR
2. Extend my current ancestry visa and then apply for ILR six months later when I can more safely guarantee approval. Ancestry visa extension costs £953 for same day service.

What does everyone think I should do?
Has anyone had success with ILR with more than 180 days absent per year?
Should I consult an immigration service for advice?

Thanks guys!!