First release of Heritage Open Days venues that need prebooking

Heritage Open Days is happening again, the chance to visit normally closed buildings across the UK, and some venues are already taking bookings. My tip with Heritage Open Days is to find a building you’re particularly keen to visit, and then look to see what else is in the area – lots of churches usually — and make a day trip of it. The search function is here.
Most of the venues are turn up on the day, but some want to control visitor numbers.
More venues will be added over th