About to order one of two Cannondale bikes

Basically a site has 2013 spec F29 Flash 1 & 2 on sale and I've always wanted a lefty (comes in at my budget of around £1,000)

I'm about 5'5 1/2 nearly 5'6 with an inseam of 29''.

2013 F29 alloy 2 is only available in Medium @ £999

2013 F29 alloy 1 is available in Small as well as Medium but is £1129

I'm using a UK cycle to work scheme which grants a voucher up to the value of £1000, however as these two bikes are on offer, the voucher is only worth £900 to cover the scheme admin costs.

So I'm wondering if the medium would be ok...and save me spending an extra £229 to get the Small in the F29 1...or at that price is it worth the extra money over the F29 2? Spec looks relatively the same on them bar brakes and tyres and a couple other things.

I rode a Boardman Pro Hardtail in a medium and it was fine...but I went to try a c'dale at a LBS (Trail 29er) and the medium seemed quite big...trying to determine if the F29 top tube slopes downwards towards the seat post enough that standover wont be an issue and save me some cash...

Bit torn on this and Im due to get the voucher on Monday next week with a view to placing order that week too.

Here's the links to the two bikes for info. I know that its always best to sit on the bike however I have no way of doing this as nowhere has these in any LBS (or similar models) in Edinburgh.

C'dale flash F29 2
CANNONDALE F29 2 (FLASH ALLOY) 2013 :: £999.99 :: Mountain Bikes :: Front Suspension 29ers :: Pauls Cycles

C'dale flash F29 1
CANNONDALE F29 1 (FLASH ALLOY) 2013 :: £1129.99 :: Mountain Bikes :: Front Suspension 29ers :: Pauls Cycles

Any help would be appreciated