If you're planning to go to IETF 101 in London, by far the fastest and
easiest way to get from Heathrow to the Metropole is to take the Heathrow
Express to Paddington in 15 minutes, then a 10 minute walk to the hotel or
if you have too much baggage, a very short taxi trip.
The downside is that the HeX is absurdly overpriced, walk up price £27.
But if you buy your tickets ahead it's a lot cheaper. It's too late for
the 90 day advance fares, but you can get 30 day advance for £8.80 if
you'll be arriving Sat or Sun or £14.30 if you're arriving during the
week.
Buy here with a credit card: https://www.heathrowexpress.com/
You can take the underground which is cheaper, but is much slower and
requires a change at Hammersmith or Earl's Court.
R's,
John
PS: For people with a horror of public transportation I'd suggest an app
called Gett which is like Uber except that it hails real licensed black
cabs rather than random guys without insurance. It's also like Uber in
that they run at a loss and often pay the driver more than they charge
you.
PPS: If you want to go to the theatre, you might want to check those
tickets too. Hamilton is hopeless, sold out in January, but there's lots
of other shows.