I assume you have been charged the full amount for the intended itinerary?

Well, SPTS will try to get you on your original flight. Or a reasonable alternative. Or offer you a refund. Play nice with these guys - they are the real deal and will do their best for you. If they can't do it, then, it cannot be done.

Then, and only then, you get (mildly) stroppy with and demand your flight be reinstated as it was booked and paid for - and any changes, cockups of IT SNAFUs are their responsibility. They'll know this anyway. Be cheeky and ask them to put you in a different cabin if economy is not available.

As for compo - I suggest you ask for nothing. If you get what you paid for, then that's that. If you don't get it and they ruin your holiday or cost you a fortune making alternative arrangements, I suggest you ask them for the name of their legal representative.