Gary wrote:
If I get the sleeve flush to the front of the plasterboard the sleeve won't
be deep enough into the wall to be into the breezeblock, this would be the
problem. These are also the largest bolts I found (length wise).

I now have one bolt in the wall as described in my earlier post. Is there
anything I could use to fill the gap whilst still using the bolt as secured?

The problem, as I see it, is that you have this gap between the
breezeblock wall (which we'll pretend is 'strong' for current purposes!)
with a bit of air followed by the plasterboard. The plasterboard's not
very far off the breezeblock, is it - what, half an inch or an inch, the
thickness of the dabs, right?

For a firm fixing, I'd want to bridge that gap with something more
solid, or attach the brackets which holds your TV up flat against the
breezeblock itself. Suitable 'packing' might be: wood offcuts, the
car-body-filler that at least one of our regulars is always keen on, or
similar gubbins. One other poster's already suggested losing the sleeve
anchors and using the polyester-resin-and-studding approach, which would
be OK if you can spread the load onto a large enough area of the
more-or-less-unsupported plasterboard left at the front.

HTH - Stefek