My view regarding fire rated down lights is that surely because I am damaging the fire withstanding properties of the plasterboard ceiling, regardless of whether it is designed as such then steps should be taken to repair it to its previous standard of fire resistivity
I'm sure Building Control would have something similar to say.
Personally I'd appreciate a bit more time to get out of a property if I was upstairs and a fire was in a room below, the fire is surely going to come roaring through into the ceiling void in no time without fire rated fittings.
I think the only job I've ever done that HAD to have fire rated fittings was where a customer wanted down lights in their garage, above which was a bedroom.
Most of the integrated LED down lights these days are fire rated by default anyway.