You on that ridiculous line Elvis? No trains any weekend during November as OH found out when he tried to go to Chelsea last week, I had to drop him off at Tottenham Hale. I wasn't best pleased.
Choose King's Cross. Trains take about 48 minutes non-stop, some do stop about twice, and go every half an hour at 15 and 45 minutes past, sometimes perversely at 14 and 44. Some go on to Kings Lynn and divide at Cambridge, so sit in one of the 4 carriages nearest the barrier, otherwise, if you doze off or aren't paying attention , you could be in Ely or Watlington or somewhere! before you know it