Thanks.
Sounds like a good idea worth having a go. I guess they mostly don't have a problem with you taking a tripod round? Had to hand hold all my indoor shots at the weekend so didn't get many keepers. Went to polesden lacey as well yesterday (not an open day apparently) and they didn't allow backpacks in the house even.
I had a look at your london shots but will look at the national trust section later
On the private visits they will allow you to use a tripod, but probably not on a regular visit.
But, I was allowed to use a tripod at Shugborough Estate. I arranged the visit in advance though.
The best way to "get your foot in the door", is either write a few emails to various locations and ask if you can visit and point them in the direction of your website.
But from experience, you'll need to email them at least 2 or 3 times asking, because they never seem to answer any emails straight away.
Just keep pestering them, to wear them down
Or visit a location when it's open to the public, shoot some photos and ask when you're at the location if you could come back on a private visit.
Shooting hand held at high ISO's is really a waste of time, because some locations are too dark inside.
On a private visit, you can open and close curtains and move the guide ropes etc.
Once you've been to one location on a private visit and got the photos on your site, I think you've got more chance of other locations saying "yes" after you've told them about the private visit(s) and shown them the photos.
Good luck with the visits
Thanks for looking at my site