Not sure if these are the answers you are looking for but here goes.
It's pretty certain that BA's final salary scheme (NAPS) will close next year.
Any benefits accrued by the members of that scheme are protected and cannot be taken away or changed. Any new scheme agreed will take effect when the old one is closed and then be ongoing.
I'm pretty sure that this will be the case with Rentokill but I'm not sure of their situation.
At the end of the day it's sad to see these schemes go, but would you rather see the scheme go...or the company?
So.... go buy yourself a second property and stick it into the new SIPS scheme next year.
Hope this helps.