He should go nowhere near her official residence, good decision.
When Theresa May went, the ill-mannered Sturgeon stood arrogantly on the threshold at the top of the steps & made not the slightest gesture to move towards her to welcome her, having her climb the steps up towards her. Approaching visitors to welcome them is a common courtesy the world over.
No president of the US, France or anywhere would do that. You think Boris is a 'buffoon', you are entitled to your opinion, but he is well-mannered & would never do such a thing.