We got upgraded to business a couple of years ago, on a flight to USA.
Heathrow lounge was superb, quiet and comfy seats, and help yourself to a selection of malt whiskys.
Flight experience was a different story. The ‘herringbone’ layout means you have to choose betweem raising the side claustrophobic partitions, or a chance to chat with somebody else’s feet. Staff were inattentive and boderline rude, compare to an upgrade on American Airlines a few years ago.
That earlier AA experience was monumental. A huge area to call your own, and just snap your fingers and more champagne or ice cream, or whatever, arrived. BA was a disappointment in comparison, basically just staggered zig-zag seating and a posher looking menu, served by slightly begrudging stewards and stewardesses.
Make sure you are not near the back of business class, else you might be just a few feet away from the unavoidable screaming babies that are usually positioned on bulkheads at front end of cattle class.