Nice one. All worked out very well. Thanks very much for advice.I’d suggest come into Brighton on Dyke Road. Park at top of The Droveway (I think it’s still free there). Walk down The Drove to Preston Park.
Bit of a hike back up the hill back to the car (but you’re not the one running) but then easy drive down to Portland Road (metered parking). Walk down onto New Church Road/roads downto sea front - they’ll run to and fro four times here so good place to watch them.then walk along sea front to finish.
Getting accross Brighton will be very difficult other than using the a27.