If you want to knock off some miles and move to parking in Taunton we could use the car park by the up side of the railway station. It's a council car park, and the last time I used it on a Sunday (OK that was last year) it was free.
We could re-join your route by riding up Kingston Road to Kingston St Mary, which isn't too steep - and presumably a similar cut through on the way back.
Again there's a cafe at the station on the main up platform, but I don't know if it's open on Sundays or what their response to a load of thirsty cyclists would be! There are plenty of other options in Taunton.