@Elderflower - if inside all day you don't have to apply so often at all - that every-2-hour rule is for if one is going to be outside for a good while, especially in challenging situations. In the latter(save for swimming at the beach which is seldom these days)I tend to cover up more rather than slathering my whole body with sunblock - I just save it for exposed areas. For myself as far as indoors, since I don't have to work outside the home, I'm able to wait until not long before I head out of the door for incidental exposure to apply both my sunblock and makeup, thus only one application for the day. Hope this helps!
If your skin will tolerate chemical sunblocks, the Neutrogena Sheer Dry Touch series are good, esp. the 55 and the 70. I was a big fan of the 70 up until I had my skin disaster from another product and couldn't use much in the way of chemical ones any more. However, the chemical+physical combo in the CeraVe AM SPF 30 seem to be fine on my skin for daily use. Still, for more challenging situations I'd find a higher SPF plus a hat. The combo of a hat and the sunblock really do make a difference. Another thing to consider is the use of anti-oxidants or Vitamin C in the morning(topical use)which will boost the sun protection power of whatever sunblock you end up using. Also, EAT your anti-oxidants in the way of dark green foods and a lot of brightly-colored raw produce in general. But the dark greens are super for this.
Hope all this helps!