My brain hurts. Planning trips up and down the tidal Thames is not as easy at it might first appear. Doing a bit of homework seems to be something of a neccessity if you are any kind of tight schedule.
Normal lock opening hours where the canal meets the Thames at Brentford are between 8 am and 6pm, but only two hours either side of high tide. In practice that sometimes means only an hour and a half opening that day e.g if high tide is 7.30 am they're only open from 8 am to 9.30 and you wouldn't want to go out after about 8.30 to go upstream because you'd be running against the increasing outward tide strength. To make matters more complicated you have to look up the time for high tide at London Bridge, then add an hour for Brentford, then add another hour for Summer Time.
Going up stream next week we'll be OK as high tides are early afternoon, but coming back the following week we might have to make an early morning exit on to the tideway at Teddington. That also means we'll have to moor overnight at Teddington Lock (which might be nice anyway).
None of this is really a big problem because you can request to lock through Brentford outside of normal opening hours, but we'd rather not.
We were also concerned about getting under Brentford High Street Bridge which has insufficient headroom at high tide. However I now understand it is only a problem at the height of the tide, and we'll be going out 2 hours before high tide, so that's OK.
Have you got all that? Forewarned is forearmed as they say.