Forgive me father(s) for I am about to sin...

I'm contemplating flying non *A in a (currently) hypothetical trip to Oz. To get there on miles in F I'd be looking at 100k + £340 + taxes each. That's a lot of miles (which I don't currently have). Alternatively, I could be tempted by:

GLA-LHR-DAM return in BD Biz for 20k + £140 + taxes each (Gold redemption upgrade from Y)

DAM-DXB-SYD-DXB-DAM on EK First for... £1681 each including taxes!

That seems a stonking deal - the only downside is I can't seem to find a decent deal on QR in its place so I can get DC miles!!

Any thoughts - it seems that for a pretty reasonable amount I can get paid (restricted) first on a decent airline and experience what I've been led to believe is a good F lounge in DXB and decent F-in-the-air service on board. Net of the cash part of cash+miles it'd cost me an extra £1481 each (less than that in reality due to increased taxes ex UK - so perhaps as little as £1400ish) but I'd save 80k miles each.

This works out at c. 1.75p per mile - is that worth doing??