Hi Stockie, either bike will be fine - they're both well known and proven models. If its the Roubaix Sport (£1350 in the sales?) you are looking at compared to the Domane 4.5 (£1800 in the sales?), the equipment levels on the Domane are (IMO) far superior, though both have compact chainsets and similar gearing which will be fine for the hills. Several of my friends ride Treks and are very happy with them, and we're about to buy one for my son for Xmas.
Couple of other thoughts. If you are interested in a Trek, have a look into Stanley Fearns
www.stanleyfearns.co.uk/ in Matlock - prices will be similar to the big chains, but the service is outstanding. Also you might want to have a look a Planet X in Rotherham, especially the Ultegra equipped bike they are doing for sub £1000 - fantastic value for money:
www.planet-x-bikes.co.uk/i/q/CBPXSLPULT2/planet_x_pro_carbon_shimano_ultegra_road_bike
I ride the SRAM equipped version of this and while it doesn't ride quite as well as some of my other bikes, it's still a great bike.
Hope that helps,
Andy