Try the UK Automobile Association. The AA in UK will issue a carnet for non-UK residents and non-UK vehicles.
You can't reach the carnet department via their website, but you can reach them at +44-1256-493753 or by E-Mail to: firstname.lastname@example.org
. They can fax the application forms to you, but will require originals to be mailed back to them before issuing the carnet, so allow time for that.
Alternatively try the RAC (also UK), which also can't be reached via the website, or by e-mail, but you can "Speak to the wonderfully helpful Sue Collins 01454 208000 ext 33837."
Good luck, let us know if that works.
"It matters not what goal you seek
Its secret here reposes:
You've got to dig from week to week
To get Results or Roses."
'One world, two wheels'