It may just be that all that's needed is cleaning & lubrication of the moving parts of the brake assemblies to get everything moving freely.
There's no problem with fitting new pads without replacing the discs, providing the discs are in acceptable condition - it seems likely that they are OK, as if they weren't the MoT should have picked up on that, even if only as an advisory. Bedding-in will not be noticeably worse than with new discs.
Modern pads are not necessarily "harder" than old, asbestos-based pads. "Hard" & "soft" refer to friction level - modern pads cover just as wide a friction range as asbestos pads did, probably even wider. Modern pads are, however, more "aggressive", i.e. they tend to be more abrasive, which means they wear the discs more rapidly
Where are we going & why am I in this handcart?