Many thanks people. It does help to hear the kind words and stories, really it does.
I was riding most of yesterday and already I am finding that I am able to think about what has happened without it upsetting me. It still hurts, there is still loss but I'm not getting so emotional over it. I suspect it will be like that for ever more.
Last night, my wife showed me some video she'd taken of the 2 dogs playing. It made me smile to see Titi bounding around. It's stating the obvious I know but I feel I shall remember him with smiles and not just grief.
There is a noticeable change in our other dog, Tess. She is quieter and more withdrawn. I guess she knows something is different but who knows whether she knows what it is. She'll be right as rain in a few days, I'm sure, but right now she's getting a bit of extra attention!
RIP Titi, you are missed.