Jonathan wrote:

So, the tv isn't THAT heavy, but the concrete is just not giving! I drilled
a smaller pilot hole (took 5 minutes to go 1" with a 5mm bit) but when it
came to the 8mm bit, really nothing was happening. I gave up after about 15
minutes and 3mm having gone slightly deaf!

It sounds like you had found the steel. Even an SDS won't drill through
that.

You might try a steel drill but be prepared to throw that away. But it
will be cheaper than buying an SDS then finding you still have the
problem.

Where exactly is the concrete?