Compared to the cattle-car coach class on BA (we just flew to Heathrow a month ago) 1st class WILL be a huge upgrade.
Goodness, the seat (with video!) in from of me was less than a foot away. 9 hours of cramped quarters... and I'm a fairly short guy. Horribly uncomfortable seats. Yeah, coach really sucked.
If you’re flying BA, check out their coach plus class of service. It costs a little less than twice the price of a steerage seat and you get a very nice seat that’s pretty much the equivalent of a domestic US first class seat. I know; I’ve flown in both classes.