Research ... a few hours. Say three. Email exchange: not much. Visits: 2.5 hours travel time each journey (KCH is on the other side of London from E17), which was one two-hour appointment for "why are you doing this?", blood test and test sperm donation, a one-hour "are you absolutely OK with the ethical details of this?" (which leads me to think that people donating then changing their mind, which you can do any time until the donation is actually used, is a major pain in the backside for them), and four visits so far for actual donations (about 15 min each). Total including travel, which was most of it: 22 hours, if I've counted correctly.