Your ever-expanding web resource for the Raleigh Twenty and other classic small-wheel bicycles.
I think I need a longer seat-post
The stock seat-post that comes with the Raleigh Twenty is 28.6mm chromed steel. It's long enough for people up to about 175cm or 5'9" tall. Of course, this will also depend on what saddle you have on top.
Tranz-X offers a 28.6mm seat-post in 350mm length. Usually only available in black.
Kalloy makes a 350mm and 400mm long 28.6mm seat-post. Most bike shops can order it in.