Help mounting TV on dot and dab wall

I'm struggling to mount my TV on my wall. I'm pretty sure that I have a dot and dab wall, with the plasterboard and cavity measuring a combined depth of 25mm and then i'm able to drill another 40mm into the solid wall before i hit something hard that I can't drill through (presumably a rebar).

I have these fittings, which require you to drill 49mm into the solid wall so that the sleeve anchor part fits into it.

I've not been able to find any fittings that require a shallower depth and are suitable for a heavy TV and a cavity wall.

Any help and advice would be much appreciated!