I'm OK with my M-type Brompton but was curious if Brompton will make the part available as they have the reputation of making things backwards compatible. Got an email from B this morning confirming all:
"The new H type handlebar uses a different length handlebar support along with a standard M type bar.
This arrangement can be retro fitted to an existing bike, in order to do this you will need to replace the handlebar support and brake/gear cables. If your bike does not have the 30 degree brake levers fitted then you will also need to replace these.
If your bike is an M type you can reuse the existing handlebars, though we do recommend replacing the bars periodically so if the bars are damaged or have been used for more than 5000 miles you should also replace these.
If converting from an S or P type the handlebars will need replacing with a set of M type bars.
The new parts can be ordered from any Brompton dealer and will be available from early 2012.
I'm assuming Brompton doesn't mind me sharing this email with our group.