I’m assuming that as you’re commuting you will want something that comfortably takes guards and 25mm tyres (more grip, more comfort – some say less rolling resistance – than 23mm). Also you will want to be able to afix a nice, lightweight rack to the back, cause if you’re doing 20 miles each way (or even 10) you’ll not want to be carrying your gear in a backpack, gets awfully sweaty and that.
But being a keen cyclist, you’ll also want something that whilst comfortable for those long, long rides, is also light and fast, so that in the summer you can whip the guards off and race it happily in a sportive or somesuch.
Look no further than the Kinesis Racelight. It’s almost the default choice as a 2nd (read winter) bike for serious roadies. A very good, lightweight frame with superb build quality, strong as an ox, stiff in all the right places, yet compliant and comfortable enough. you can pick them up for £1,100 or so from Kinesis and you can use the change to upgrade the wheels should you feel the need.
The other choice is the Cannondale Synapse which won the Cycling Plus 2014 bike of the year. But I’d go for the Kinesis, I’ve got one and wouldn’t swap it for anything