I've had a look on the Leger website and there is no mention of the HB plans on there, but I'm not convinced that they don't provide them, as there's also no mention that I can find of Character Dining either and I know that definately up until Nov 07 Cafe Mickey, Lucky Nugget etc. were available as a bookable extra.
I've booked several trips through Leger, but always direct with them and interestingly we had a type of HB meal plan through them in 2004, long before the current HB option became so popular. Have you actually paid any money to Thomas Cook yet, if not I'd definately explore the other options available for booking DLP, you may even find you save some money doing it yourself.