The maths just doesn't add up, the ROI on this unit is just not worth it.
Why not just buy 5 ANT Miners?
5 x 180GH/s = 900GH/s - That's without over clocking.
That will set you back just under 5BTC (They are 0.99BTC each including shipping) or at current exchange rates on coindesk $3155 or £1900.
Plus PSUs, plus VAT at the border, and the usual exorbitant "handling fees" for the privilege of charging you that VAT.
VAT alone is another 20%, PSUs for 5 miners, depends how much quality you want but I'd expect anything from £100 to £300 to power 5 ants.
You forget the most important part: S1's are available RIGHT NOW. Even with the extra costs, it's still way more interesting just due the fact that you can start mining 3-4 days after ordering.
IF 5 S1's end up more expensive than this, you will still make it up big time because you can already start mining.