NoPaddle

We are hoping to convert an external porch to an internal porch with downstairs toilet. The existing porch has brick columns shown in the image below that contribute to the properties charater and so I'd like to leave them in place and exposed externally. What is the best way to deal with the insulation where the columns are, and what about penetrating and possible rising damp? I've started to sketch the design as shown below. Thoughts and advice backed with evidence and experience would be very welcome. Untitled.svg

The image below shows the property as it is now. We are planning a rear two-story extension; and detached workshop, office and studio.

We are planning an extension to our house and I am looking for advice and guidance. It is a work in progress, but this is how it looks now.