If necessary I'd be prepared to travel as far as it takes - I'm already intending to go to Warley Place, Essex, in March & Llandudno, Anglesey & the Scilly Isles in June - July.
I don't know of anywhere "local" where aconites grow, although I suppose I might just come across some on the off-chance - the Avon Gorge turned up a weird & wonderful range of aliens last season