To prevent the intrusion of water into your brand new conservatory, a horizontal damp proof course (DPC) should be installed in the conservatory walls, and it has be continuous with the main house wall construction to prevent any leaks (i.e. no gaps).
Cavity trays (a DPC that steps across the cavity) and suitable external flashings (pieces of material that cover tiles and extend up the wall) must be provided where the conservatory roof touches the main house wall in the same way as if you were building a normal tiled or flat-roofed extension.
You need to pay close attention to damp proofing details where the conservatory walls meet the existing house walls to stop water getting in and damaging your existing structure.
If the conservatory windows sit against the main house wall (either as a combined full height window or door off the DPC or above a dwarf wall (the low brick wall shown in the picture above) then an insulated vertical DPC cavity closer (which acts as a seal, preventing external water and damp from entering the wall) should be provided.
The conservatory floor should also have a damp proof membrane which is linked to the horizontal DPC.