The Doctor doesn't normally do the domestic thing. But, he did have Christmas dinner at the Powell Estate, and fish-n-chips with Rose whenever they were on a world that had it, so it's not like he doesn't ever.

And this is Sarah Jane, after all. So, he's happy to give it a go. He knocks on the door with one hand, the other holding a small vase with some exotic flowers he'd gotten from the gardens outside (with permission, of course).