Forecast shite for Thurs pm, better Friday although still plenty of showers about.
I'm finishing at 12.30 on Thurs, so you can guarantee it'll start pissing down at about 1.30.
BBC forecast has less than 15% chance of rain in each hour block before 4pm, and 25% in each block thereafter.
Should be fine on that basis.
It does make 'bat first' a less obvious choice if the forecast worsens though.