Adding Gite activity to existing auto entrepreneur registration

I have been registered as an auto entrepreneur since 2012 under APE code 8121Z - nettoyage courant des bâtiments. I now wish to scale back this work and operate a gite, via a second property which I am jointly purchasing with my wife. I also receive a small monthly UK government pension on which I pay income tax within the UK. I expect the gite earnings to be the main source of income here in France.

Am I correct in thinking that I can simply add a suitable APE code (perhaps 55.20z?) to my existing auto-entrepreneur registration to cover the gite business and if so, how I go about doing so?

Additionally, could you please confirm that:

1. I would continue to make trimestriel payments via Net Entreprise but at the reduced rate of 13.215% and not at the Artisan rate which I have been paying thus far,
2. our existing Health cover entitlements should be unaffected by the changes, and
3. I would not be required to pay CSG also (which I think only applies to LMNPs)?

Although I’ve read about a greater abatement for Income Tax purposes by having the gite classified as a meublé de tourisme (71% in lieu of 50%), is there any similar reduction in the level of social charges?

Many thanks Valérie.