I would add a washered screw (or flange headed) to the top of each slotted hole before trying to change the fill valve.
It’s one of those : either do the least possible so as not to disturb anything from its current position ( eg flush pipe seals, pan connector);
Or - take cistern right out and refit with new internals and new seals everywhere.
A decision best taken on site.
It’s one of those : either do the least possible so as not to disturb anything from its current position ( eg flush pipe seals, pan connector);
Or - take cistern right out and refit with new internals and new seals everywhere.
A decision best taken on site.