Direct to Tesla or a second hand dealership?

Solar has gone up, power wall 3 installed, next on the list is to get the EV.

I love the look of the model Y, it suits life with the SUV due to kids and needing to lug stuff around.

I’ve had a good look around online for what I can get for my budget. Autotrader has a fair few under the £21500 I’ve given myself. Whilst Tesla direct doesn’t have many for that budget, I’d be willing to go slightly over due to the warranty that comes directly with them.

Just after some real world examples of purchasing from both Tesla and from second hand dealers.

Is one better than the other?

What to really check for with dealerships over Tesla etc.

Cheers!

Edit: if anyone can give details of a good and reliable dealership to look at I’m open to travelling to collect from West Sussex