"I would be pointing to average earnings rises."
Which have only happened because of very low inflation, under 1 %, over the last 2 years. Prior to that real wage growth negative as inflation was higher than wage rises.
The NLW has been responsible for a big rise in % increase for the lowest paid, BUT its not going to be repeated next year and has already been accounted for.
The Poles that you speak of are a very small amount of people really, the vast majority of EU migrants are permanent settlers.