I console myself by remembering it's a problem shared - not least by the American writer P. J. O'Rourke, who had this to say about it:
"Usually, writers will do anything to avoid writing. For instance, the previous sentence was written at one o'clock this afternoon. It is now a quarter to four. I have spent the past two hours and forty-five minutes sorting my neckties by width, looking up the word "paisley" in three dictionaries, attempting to find the town of that name on 'The New York Times Atlas of the World' map of Scotland, sorting my reference books by width, trying to get the bookcase to stop wobbling by stuffing a matchbook cover under its corner, dialing the telephone number on the matchbook cover to see if I should take computer courses at night, looking at the computer ads in the newspaper and deciding to buy a computer because writing seems to be so diffficult on my old Remington, reading an interesting article on sorghum farming in Uruguay that was in the newpaper next to the computer ads, cutting that and other interesting articles out of the newspaper, sorting - by width - all the interesting articles I've cut out of newspapers recently, fastening them neatly together with paper clips and making a very attractive paper clip necklace and bracelet set, which I will present to my girlfriend as soon as she comes home from the three-hour low-impact aerobic workout that I made her go to so that I could have some time alone to write."
Update this with more recent distractions - taking 'just a few minutes' to play a game of Freecell , or 'just a few minutes' to check online headlines, and then a few minutes more to follow an interesting link etc etc A whole morning/afternoon/evening can be idled away. Enough! Even writing this is procrastination. Back to work!