lime and vermiculite

I've had the local Conservation Surveyor round this morning (deep joy). It looks like I have to go with Listed Building exemption to Part L for thermal elements and have the external walls re-plastered with lime-based plaster. His suggestion was to mix it with vermiculite to give some thermal improvement. The plaster depth should come up to the original window architraves.

Some of the wall has already had cement-based render applied by a previous owner. He wants this taken off and replaced with the lime/vermiculite. The wall is about as straight as a snake.

Is this a specialist job? If so, what should I be looking out for?

Not really a specialist job! you will need to find a plasterer who has done lime plastering as most of the up coming plasterers would not know the difference between lime and a lemon .