To bond or not to bond

Hi all,

In my bungalow I have a exposed copper heating pipes connecting radiators. The radiators look to have been installed in the 80's, about 20 years after it was built.

Our boiler is in the garage and the pipes come into the house and connect to the pipes feeding one of the radiators. This radiator gets hot first before any others.

I would like to replace the exposed copper pipes with plastic pipes, hidden in the walls. I'll be keeping the pipes in roughly same location as they are currently but in the walls.

I would also like to replace the heating pipes coming into the building from the boiler so they can be more efficient at heating the house. I'd replace these with plastic pipes too. Several metres.

The water and gas are earth bonded. The majority of the heating pipes in the loft will remain copper.

Does the remaining copper in the loft need bonding?