I am scheduled to arrive on 12/20 (Friday) at Heathrow at 11:10 AM. I will purchase an Oyster card and head to my hotel near St. Pancras station. Do any of you have any suggestions for a convenient place to purchase a SIM card? I will use my phone in London and in Germany. I have found a few possibilities from other posts but don't know the city at all so am unsure which might really be the easiest to access. I do plan to get out and walk/explore some to help with jet lag - maybe near Hyde Park as I understand there is a Christmas festival there - but I am open to other suggestions as well.
Thanks again for all of your help!