If that "big boys product" has the same range issues as the Evohome then it would be more trouble than it's worth even for big homes.

We have 23 zones but need 3 controllers because of the lack of range and any sort of plug in booster device from Honeywell.

It does seem rather daft that a product which offers greater benefits and energy saving the larger the install is so hamstrung by range, and there is no simple solution to boost it.

It's not too much of a problem having multiple controllers as we just named them downstairs, upstairs and upstairs 2, other than they all need to be within range of the boiler relays. So again depending on the location of the boiler controls and the furthest radiator away, range could be an issue.