Naming parts on export

Hello, I've written a piece and had to use the stock names for parts to get them in the right key for brassband. I've then edited the names of each part to suit the brassband - ie- original was Alto Sax - I've changed this to Tenor Horn as there was no tenor horn in Eb in the original instrument list.
But... when I come to export each part to print as a pdf, the instrument written at the top of each part reverts back to the original ie Alto Sax.
Very frustrating as when export the whole score as a pdf for printing it shows up as my changes - ie, all the brassband instruments!
Screenshots attached to explain hopefully.
So I'm just after saving my changes of instrument text on each individual part.
Thanks.