For the most comfortable reach, your nightstand should sit level with your...

https://fionafreshmaids.com/the-ultimate-guide-choosing-the-perfect-bedside-table-height-for-a-65-cm-mattress/

For the most comfortable reach, your nightstand should sit level with your mattress top or up to 10 cm below it. Most UK beds work best with a table height between 55 and 70 cm