In the 12 years I have held a PPL, I have used the training fix facility once.
At the time, I was very low houred and couldn't establish a precise visual fix in haze over featureless terrain near controlled airspace near Stansted.
30 seconds later, my position was confirmed, allowing me to make sure that I avoided a transgression that could have caused airline flights to be sent around and/or held.
It also helped me to learn safely about one of the pitfall of visual navigation and I took a couple of lessons in beacon tracking (this being before reliable GPS was available as a backup.)
IMHO the service is worth its weight in gold, a position the CAA seem to share.