Well the tube from the Hoover Junior and Senior that holds the bag on would bend down, so you just had to carefully remove the bag to ensure no dust falls out. The Powerplus is the Senior-Ranger-updated model and Id imagine the fill tube was located at the top.
Im not sure when Hoover UK started to have top fill uprights, I know the Junior U1012 (another favourite of mine) had a top fill dust tube and that dates from 1976. Hoover's last updated Junior U1104 also had a top fill tube that sat with the Powerplus, range wise - those were the "last of the classic uprights" as Hoover called them before the Turbopower series took over in 1987, but even the Junior U1104 sold alongside that range.
I am not sure if there are any modern uprights that are bottom fill now. Only one that I can think of that is bottom fill would be my Miele S162 Alternative stick vac and as far as I'm aware that still sells in other EU countries and the U.S