I have purchased an iPhone SE but there is no charger

Not correct. No iPhone is micro USB.

The iPhone SE comes with a lightning connector in the phone.

The cable supplied with the SE is lightning to USBC.

As documented below, which is from the Apple Website -

In the Box

• iPhone with iOS 14
• USB-C to Lightning Cable
• Documentation

If you have an old charger which is lightning to USBA you can still use that.

You can use any cable as long as one end is lightning connector which goes into the phone

The point is, a lot more people use USBC chargers or have a MacBook.

It does not come with a charger anymore.

It does explain this on the apple website

iPhone SE - Technical Specifications - Apple

In the Box

• iPhone with iOS 14
• USB-C to Lightning Cable
• Documentation

You don't have to buy a separate charger.

You can use an old charger as long as it has a lightning cable.

Nobody has said you have to use the cable in the box

You said you had a working cable all ready.

iPhone SE - Technical Specifications - Apple

In the Box

• iPhone with iOS 14
• USB-C to Lightning Cable
• Documentation

So whats the issue?

If you look on the apple website it clearly explains what is in the box.

More phones will stop coming with chargers.

I am not sure what your issue is, when you have a charger which works

Of course it won't, USBA and USBC is different, clue is in the name and size of the connectors.

You said - "Ok then USBC doesn’t fit an Apple USBA plug which I have from my old SE"

So you have a working cable as an old SE would have used lightning, so you can use that.

Whats the issue? You have a working charger

If you have the cable and cube from your iPhone SE, use that.