Having just ran through the local forecasts the worst of the rain (rated as heavy) appears to be on the southern part of the loop between 0400-0700. Nearer the start it is rated as light showers/moderate rain.
Between 1000-1300 there is a risk of thunderstorms again on the southern part of the loop, mist likely when most will hit the climbs, but the rain at these times is actually limited to less than 1cm over the 3 hour window.
The return to London looks like showers.
Winds do switch round about 0900 onwards from a South Easterly direction to a stronger South Westerly wind, but that will help the final stint!
It looks like they now anticipate the bulk of the storm to be south of the projected tracks that were available yesterday, which is a good thing.