Thanks Dave!
Last I saw of the French Mil heli-rodent as I wandered home through the woods, it had tracked through the heli-lanes to around Richmond, then headed SW towards Midhurst, then SE towards Worthing/Shoreham. No idea if it landed anywhere but looked like it might be a NavEx/nice day out at the French tax payers' expense!
Edit: looks like it popped into Shoreham for fuel.