Enduro, Thanks for your response. to my honing suggestion.
When you do go back and take a second look, consider this to save you some time and stripper.
Hone it from the very start, forget the fact that its covered in sealer and crud. If you use your diamond honer, say with a 120 grit pads to start, that will remove the basic top coating [ You could use 60 grit if its really rough but be carefull as it might add some deep groves] then switch to 400 and then if they need a polished / smooth finish that is not far away from what you might expect on say a polished limestone or similar, you could add 800.
By doing it this way rather than stripper and hard graft first, you are bound to save time although your diamond pads will not be cheap, but you might save £100 on stripper!
On the sealer side, I might try LTP MATTSTONE on a sample of concrete honed to same finish - three or four coats, thinning the first down. I use it from time to time, why then client wants it sealed, but needs s finish that looks it has not been sealed at all.
I would like to know what you decide on and maybe a report / follow when its done. I like things like this, projects that are away from the norm where you have to think 'outside of the box 'so to speak.
Good luck with it