Thanks for the recent review. I almost booked this last time but ended up going with Trafalgar St. James.
I have never received a Diamond upgrade to a suite in London. I've always been upgraded to Deluxe or Executive and from there would have to pay for the suite upgrade. The only time I got a "suite" upgrade with Hilton was at the Waldorf Rome Cavalieri and that was to a Vista Suite (which is a jumbo room with seating area in same room as bed. Forever grateful for it because it was quite luxurious.)