Have a lay over and thought it might be good to make use of the time.
Flying in and out of Heathrow, on the way to Venice.
Is there any place to stay that is clean and comfortable plus an attraction in that short of time.
Or a little charming place to adjust to the time before we head to Venice for 2 nights, then boarding a Viking ship for a week of exploration.
Define charming.
Personally I take the Elizabeth Line into Paddington Station. Book overnight in the Paddington Premier Inn or Hilton. Then use the London Underground. Take Circle Line from Paddington to Westminster. Exit at Westminster. Wander about Parliament Square then follow Birdcage Walk adjacent to St James Park up to Buckingham Palace. If the Royal Standard is flying means the King is in residence. From the Palace you can walk over to and through Green Park to Piccadilly and turn right. Walk by the Ritz and Woolsley to Fortum and Mason. Shop. Then keep on walking to the crowded madness of Piccadilly Circus. If still wanting to explore instead of rest then by all means continue to Trafalgar Square for iconic photos of the Lions, Lord Nelson’s Column and the British Museum. Walk behind the British Museum into Leicester Square, then over to Covent Garden.
That would be Day 1
Day 2 enjoy a nice breakfast then take a river cruise to Greenwhich. Explore Greenwich and make the hike to the Observatory . Enroute or before boarding the boat I’d stop at a Pret a Manger for a sandwich and crisps, or a Tescos or Sainsbury for a meal deal. That way you could picnic in Greenwich Park. I’d also make the time to enjoy the extremely well done National Maritime Museum and explore the grounds of the old Naval College.
Day 3 I’d explore the street art in Shoreditch. Interesting neighborhood .
If you don't need to go into central London, consider staying in Chiswick. It is an affluent area with many nice cafes, pubs, and restaurants. We stayed 2 nights at room2 Chiswick hometel near Turnham Green tube. We visited the Hogarth House, St Nicholas church, and walked along the Thames. The next day we walked to Chiswick House & Gardens. We also wanted to take the Fuller's Brewery tour but it was already sold out.
You’re welcome.
If you have not been to London before, I would prioritize one attraction that you most want to see-for me, that would be, in no order, British Museum, Tower of London or Westminster Abbey. I would have tea at either the Wolseley or Fortnum and Mason on the afternoon you get there and I assume either one would require a reservation.