john west wrote:

The signal strength is 63% according to the signal strength meter on our
Humax DTRT2000 digi box.

Although these built-in meters don't mean much that sounds dodgy to me.
In general Humax DTT boxes need to be showing more like 90% to work
properly (I was a Humax dealer before I retired).

The new Aerial put up on the wall
Do you mean low down, relative to surrounding rooftops? Does it look
over a main road?

facing the transmitter is from
Blake-UK and of the type recommended for use with the Crystal Palace
Transmitter.
What type is it? Who installed it? Does it have a masthead amplifier?

Bill