Excuse the stupidity, but should I have bought 3×1v LEDs (run in parallel) to work with the 3v battery?

There aren't any LEDs with a nominal voltage of 1V. If you're stuck with a 3V battery and the LEDs you use aren't bright enough, you could try boosting the voltage. But that comes with a price.

 

If you run LEDs in parallel, if you want the same brightness out of each one,
you pretty much need to match current thru each. So you either drive each
one with a current source or you use series R with each led.

Problem with just series R approach is that unless you match LEDs on the bench
at a given current their inherent manufacturing tolerances are quite poor LED to
LED. So series R helps but is a compromise.

A better approach is to use a boost converter for the battery and run LEDs in series.

https://www.banggood.com/DC-DC-3V-3...-p-1166673.html?rmmds=search&cur_warehouse=CN


Regards, Dana.

 

Caution!
I was 14 years old when I made some around and around blinkers with neon light bulbs and a 90V battery. I embedded them in clear acrylic. The first one blew up so I recalled the other ones I sold and drilled vent holes in them.
Batteries fart (let off gasses).

 

Caution!
I was 14 years old when I made some around and around blinkers with neon light bulbs and a 90V battery. I embedded them in clear acrylic. The first one blew up so I recalled the other ones I sold and drilled vent holes in them.
Batteries fart (let off gasses).

I was into multivibrators -

 

Caution!
I was 14 years old when I made some around and around blinkers with neon light bulbs and a 90V battery. I embedded them in clear acrylic. The first one blew up so I recalled the other ones I sold and drilled vent holes in them.
Batteries fart (let off gasses).

Thanks for the warning!
I was only planning on embedding the components in epoxy and the back of the battery holder. I drilled a hole in the top of the battery holder to allow a small screwdriver to slide behind the battery and push it out in order to change it when it's depleted. Very tight on space!

 

https://www.mouser.co.uk/datasheet/2/268/40001948A-1145202.pdf