I have a large side garden site on which I would like to build a new house to move into. Once built I would sell the current house (PPR) and move into new one next door. What are there cgt implications, if any?
Assuming you own a house on an acre or 1.25 acres or so and are splitting it.
You will be disposing of your PPR which you have lived in and presumably get relief under S604 "PPR Relief" ie. you have lived in it since day dot and you will sell the house and not more than 1 acre of gardens etc. It will not go unoccupied for any more than the final year of possession. It is important that you ensure the terms of PPR Relief have been met and review PPR in the context of the new build.
You will retain a certain area of the original PPR for a site of the new house. So therefore the sale of your old house is just a part disposal of your original house purchase.
Therefore if you qualify for PPR Relief on the sale of the house you should be fine bar you have left out detail.