Bath pop-up / twist waste replacement

Hello,
I have (after hours of 'persuasion', and trying every trick on the internet - smacking it with a hammer did the job in the end!) managed to free my bath's pop-up waste. It's the type that's operated by turning the overflow knob. I'm now reluctant to put it back in, in case it gets stuck again in future. The waste is in the centre-ish of the bath, so it's quite likely to be pushed in by a foot/bum/knee.

To add to the complexity, the bath is a freestanding type, not on legs, so the only way to access the underside of the waste would be through the ceiling below - so that rules out pretty much every "how to change a bath waste" hint/tip/video I can find.

So my questions are:
Is there some way to guarantee that the existing plug is unlikely to get stuck in future?
If I decide to replace just the components of the waste that are on the inside of the bath, am I going to face a real problem trying to tighten up the inner flange because I can't hold the unit that fits to the outside of the bath still?

Any help/hints/tips would be greatly appreciated!

Thanks in advance,
Paul

 

If you try to do it from inside the bath you're not gonna get it right enough to make a good seal against the bottom of the bath.

Was the bath fitted with a flexi hose to allow the bath to be lifted for remedial works, this is what we do. A few lengths of timber underneath allow you to get an arm under to secure the fitting whilst an assistant tightens from the top