Thanks everyone for all the advice.
I must say Pyrford would have been my first choice. Their website has this to say though: "We DO NOT offer any berths on a residential, or liveaboard basis." Fairly explicit I'd say. A shame because I'd love somewhere a little more rural to walk my dog.
From the sound of it though, a leisure mooring on the Slough arm of the Grand Union or nearabouts might work given that I'll be away a reasonable amount and have a house where I'm on the electoral roll. Does anyone know how often leisure moorings come up on the slough arm?
Having said all that, Tim's boatyard looks like it might be a good spot. This may be a stupid question but would it be an issue that I'd be leaving for the boats for possibly weeks at a time during the winter? I'd worry about changing levels or flooding - thinking a canal might be a better option for a newbie like me.