Cumbria, I have experimented in Word 2007 and see what you mean. Typing in Gabriola, 12 point, text seems too small. Changing to 24 point creates white space between lines, the cursor is much higher than the text.
I have found a way to get round this.
After typing text in the size you want, select it.
On the Home tab, Paragraph group, click the Line Spacing icon (4 lines with an up-and-down arrow).
Click "Line spacing options".
In Spacing section, select Line Spacing: = "Exactly" At: = "16 pt". Then click "OK".
You can fine tune the spacing by entering values larger or smaller than "16 pt".
It's a bit long winded, I hope you can make it work.