Heathrow to Kensington area

Tube is cheapest: www.tfl.gov.uk. The Picadilly line is direct to Gloucester Rd and South Kensington stations but would require a transfer to High Street Kensington, for instance.

The Heathrow Express is a 15 minute express.train to Paddington Station. It is a .5-10 minute short cab ride to Kensington.

Kensington is a large area. Where exactly so we can give better help.

97 Cromwell road SW7 4DN

That is the Holiday Inn, Kensington. Website here: http://www.hikensingtonforumhotel.co.uk/
Literally around the corner from Gloucester Road tube station. See map here: https://www.openstreetmap.org/#map=17/51.49404/-0.18451

The obvious and cheapest way is by tube (Piccadilly line), direct from Heathrow to Gloucester Road. "one seat" ride. Buy Oyster Cards at Heathrow (one per person), load each one up with cash and you have your transport for your trip. Fare Heathrow to central London is £5.10 (Mon - Fri, 06:30 - 09:30) and £3.10 (all other times).

I stayed there 25 years ago. Not sure if it still is but it used to be the tallest hotel in Europe.

Literally one block from the Gloucester Road tube station. The hotel entrance is not on Cromwell Rd but on Courtfield Rd. When you exit the tube station, turn right and go to the end of the block. That's Courtfield Rd. Turn right and you'll be at the hotel in about one or two minutes walking.