Transition from UK to France

Apologies if the scene-setting to my questions seems overly complicated; I will try and keep the questions clear!

I am a British citizen, currently employed as a Director of UK engineering Partnership; i am also an Equity Partner. At present all of my income is UK based; approximately £25kPA through PAYE, with further partnership profit share declared and taxed (heavily) in UK through self-assessment return to HMRC. I do not receive “dividends”.

For the last eight years, I have enjoyed living in France, but travelling back to the UK to work every week (with occasional days working from home in France). I own my property in France and up until now have presented as a “resident secondaire”. I now spend 4 or 5 nights a week in France, so would likely be recognised as ‘resident’ in France prior to Brexit, through Carte Sejour application.

I am about to commence the process of “retiring” from the UK business, which will see reduced UK work and income over a three-year period. I would like to balance this by establishing a diverse matrix of income streams, administered and delivered from my home in France. The future state in terms of income would hopefully look something like this.

1. Host guests in my home, on Bed & Breakfast (with optional dinner at the table with my family).
2. Lead Treks/Expeditions (as an International Mountain Leader); business administered from home in France, but treks primarily in France, Italy and Switzerland (but anywhere in world possible).
3. Online run-coaching business, administered from home in France.
4. Specialist engineering consultancy; mostly uk or international clients, desktop work in France but probably a lot of international travel for meetings and site visits etc.
5. A reducing quantum of work as employee of existing UK business, through PAYE (delivered in UK). Eventually zero.

My questions are;

1. Would it be better to complete my Carte Sejour application in advance of establishing any French business entities? I can demonstrate over 5 years in France with tax fonciere / habitation and utility bills, but would need to put health cover in place .... or would the social contribution through Gite / Chambre registration tick this box more efficiently?
2. Would i need three separate business for my trek leading, online run coaching, and technical consultancy businesses? Would this create any issues with “cumulative income”?
3. What business structures (or combinations thereof) would recommend for each of the 4 France based revenue streams?
4. In respect of UK employed/taxed income, presumably I just declare this on my French Tax return (noting I have not done one before; is there is a procedure to deal with different year end dates etc).
5. Is it best to wait until literally ready to generate income with each revenue stream, or can i set them up now and file “dormant / zero revenue” return if they take longer to get going than hoped.

I hope that is not too complicated or confusing! Happy to provide further details or clarification as required. Once I’ve worked out what needs setting up, i’ll definitely be using your services to help get it all right first time!

Many thanks

Kev