Importing goods from UK to second home

Hi

I am resident in the UK with a second home in Salgar Menorca.  Subject to Covid restrictions, I am planning to travel to Menorca by road and ferry later in the summer.  Part of the reason for doing this is to bring a few bulky household items with me.  Since the last time I did a similar trip, Brexit has happened and so I am aware that there are customs formalities.  It is, though, difficult to get precise information about the paperwork I will need in order to clear French customs at the tunnel.  It seems to be particularly difficult when I am both the exporter and the importer, but in my importer role I am not based in the EU.  Anyone know:

- what document(s) I need and where I get it/them

- to whom and when do I pay the various taxes involved, how do I contact them in the first place and how do I prove that I have paid when i arrive at French customs

- are there any further complications arising from the fact that destination country (Spain) is not the same as the one on in which I will enter the EU (France)?

- are there issues of standards compliance now - any goods that cannot be imported because they don't meet EU standards (thinking in particular of things that use gas/electricity)

- suppose I just rock up at Folkestone with a car full of stuff and no advance docs, but with evidence of value, would it be a simple matter of paying French customs on the spot with minimal fuss and then off on my way?

- is it really not worth trying to do DIY importing and would I be better ordering stuff in Spain (just seems a shame not to use the space in the car, that's all). 

Many thanks in advance for any advice

Peter