If you're keen enough to want to watch all the big races you'll need Eurosport as ITV4 only show a couple of races a year
I started watching in 1996 when I left paid employment to start working for myself during that summer but didn't have much work coming in for a couple of months so was looking for something to pass the time......and decided to watch the Tour on Eurosport.
I was pretty hooked from the start though it took me a while to understand what was happening.......all the tactics and the structure of the race........and I also didn't realise there were other races throughout the season......
But I went from that Tour to the Vuelta and haven't looked back since
For many years I worked from home but spent most of the day out and about so I used to record the afternoon cycling on video and watch it in the evening.....
Nowadays I do most of my work on the computer at home so never miss a days racing even tho' I might be working whilst it's on.........