I think it will probably depend on the fitter - as they do not work FOR C&C, but are instead recomended by C&C, it is up to you to discuss with the fitter. You are free to hire your own fitter. When we had our kitchen installed, we wanted to use a solid wood worktop sourced elsewhere, but the fitter C&C recomended said he could not install solid wood worktops as they are joined differently.
Cheers
MGL