Forget about the dates. They're ridiculously conservative, especially from M&S - often in factories where they pack the same product for different supermarkets, the M&S ones will get a day or two shorter than other supermarkets, because M&S want lower risk of food spoiling before or on the date.
Plus, as others have said, it's very likely that the milk will be fine for a few days after the date, it does not automatically go bad or become unsafe the day after the date on the bottle. Although in this hot weather, you need to be careful that it's in the fridge and your fridge is cold enough. Once the milk is well on the way to defrosting, put it in the fridge, before that, the big ice cube in the bottle will help keep the defrosted milk cool.
The milk you put in the freezer will be safe to consume for months, if not years, and when you take it out, once defrosted will behave exactly the same as the one you have been using, ie at least 3 days to be able to use it.
If your milk looks OK, smells OK and tastes OK it is OK. And if it's not, it's not necessarily unsafe to eat/drink, just that it doesn't taste nice. In the days before widespread refrigeration, people were used to dealing with slightly off milk, and there are some uses where it's perfectly safe to use the soured milk, and is actually quite useful and beneficial, eg scones.
Sadly with modern day obsession with use by dates (not a dig at you OP, but I see this so often and I'm genuinely baffled that so many people are so bound by the date on the bottle and are unable to rationally assess the safety of a product and think they have to stick rigidly to the date on the pack) this seems to have been lost.
But with your milk, it will probably get used up over the weekend and will be fine for that amount of time anyway.