Hi Nick ATS,
Like you I'm also hopefully going to get a hub geared bike for my commute of a similar distance. My commute is 9 miles each way and I do it all year around.
At present I use a Trek 7.1 FX which is about ten years old. I bought it from a friend who emigrated and he's a fair bit taller than me so it's not the ideal size for me. Plus the bike had a lot of use year round in all conditions before I got it and although the bike has served me well to date I'm saving up for a hub geared bike. I have actually borrowed a hub geared bike from a friend and I tried it on my commute and I was really happy with the hub geared bike that I tried although unfortunately it was a bit out of my price range (I tried a Genesis Day One Alfine 8 albeit a 2014 model so it was a bit different to this one as there seem to have been a fair few changes to the 2015 Genesis range
http://www.genesisbikes.co.uk/bikes/urban/urban-cross/day-one-alfine-8). The bike that I tried had a Shimano Alfine 8 hub and the gear ratio though not as big a range as on my current Trek 7.1 FX was absolutely fine for my commute. I live in a fairly flat area and apart from setting off didn't have too much use lowest gears but hopefully they'd be okay for your one large hill that is on your commute. I'd agree with BrumJim that the highest gear is not as high as on my Trek 7.1 FX but I've only noticed that on the downhills and it's not something that I found to be a problem on the flat.
I've got a few bikes on my shortlist but two bikes are on the top of my short list (which I appreciate won't be the same bikes that will appeal to everyone but I'll mention them just in case they are of any interest) and I'll start with some that aren't in my top two.
The Focus Wasgo 3.0 which I think is around £700
http://www.focus-bikes.com/gb/en/bikes/2014/cross/wasgo/wasgo-tr-30.html
If Focus bikes are of interest although these aren't on my shortlist they also do a range called "Planet/Urban" which includes hub geared bikes:-
http://www.focus-bikes.com/gb/en/bikes/2015/urban-1/planeturban-1.html
The two bikes that are the top of my shortlist are as follows and one of them was kindly brought to my attention by Pale Rider which was great because I'd not managed to find it before his help.
Cube Travel SL RF
http://www.cube.eu/uk/bikes/tour/travel/cube-travel-sl-rf-anthrazit-green-2015/
and the VSF Fahrrad Manufaktur T-500. On the link below ignore the fact that the photo shown is of the step through version because it is also available as a gents frame and I've also added a link to a shop that sells them in the UK:-
http://www.fahrradmanufaktur.de/katalog/trekking?product_id=673
http://blog.chrisbikes.co.uk/2014/02/vsf-fahrrad-manufaktur-t500-alfine-8.html
My apologies in advance because I appreciate that the right bike for each & every person is different and so what I'm after from a bike for my own commute will most probably be different from what you're after. For me I want hub gear, dynamo lights (*), mudguards and a pannier rack. However I read in your OP that you want a lighter weight machine so you'd have to look at the weight of the bikes that I've mentioned to see if they're too heavy for your consideration. Having crudely weighed my current bike it's not that different from the hub geared bikes that I'm considering and whilst I'm on my commute I'm not looking to race anyone or break any speed records so durability and other features of the bike are more important to me than weight being the top priority.
* I appreciate that there are many arguments to say that they're not necessary and can be bettered in performance by battery lights but the idea of always having them powered without having to ensure that lights/batteries are always charged appeals to me enough to want to give them a try.
On price my apologies because the Cube is £850 whereas the VSF T-500 is £900 but I'm in a similar position to you and whilst I currently have a bike that will do my commute I'm going to save a bit longer to try and get the right bike for me that will both suit my needs and last.
Comparing the Cube and VSF T-500 head to head on some of the specifications:-
Frame: Cube = Aluminium vs. T500 = Steel
Brakes: Cube = Shimano BR-M355 Hydr Disc Brake vs. T500 = Shimano BR-T4000 V-Brake
Gears (both internal hubs): Cube = Shimano Alfine SG-S7000 8 speed vs. T500 = Shimano Alfine 8 speed
Tyres: Cube = Schwalbe Marathon Supreme Kevlar 42x622 vs. T500 = Schwalbe Marathon Racer 35x622
Front light (both dynamo lights F&R): Cube = Busch & Muller Eyc T Senso Plus vs. Busch & Muller Lumotec Lyt Plus. *
Rear light: Cube = Busch & Muller Toplight View Plus vs. T500 = Busch & Muller Toplight Flat Plus
Front Hub: Cube = Shimano XT DH-T785 vs. T500 = Shimano DH-3N72 **
Weight: Cube = 13.9 kg vs. T500 = 14.8 kg
* Regarding the front light looking at the beam patterns on the website link below the Cube's B&M Eyc light looks a lot better than the B&M Lyt on the T500. Also looking online at various shops the B&M Eyc is a more expensive light that the B&M Lyt.
http://www.peterwhitecycles.com/headlights.asp
** Not that I'm an expert on dynamo hubs but looking on various websites the Cube's XT DH-T785 hub dynamo is more expensive that the T500's dynamo.
I'm not an expert in components but to me the quality of components fitted to the Cube bike seem to be better. Furthermore the Cube has disc brakes as opposed to V-Brakes on the T500. As well as the brakes being a clear difference the big difference seems to be what the frame is made of with the Cube having an aluminium frame whereas the T500 has a steel frame. The frame material is one reason why I'm having a really difficult time deciding between the two bikes. From a components/specification it's the Cube that stands out to me however the steel frame of the VSF T-500 really appeals to me from a longevity/durability point of view on a bike which for me is a daily commuter all year around.
I hope that some of the above helps but my apologies in advance if none of the bikes that I've mentioned are of interest to you.
Good luck finding the right commuter for you! I'd be interested to hear back on what you choose.
John