visit local historical sights (Pompeii for example) - yeah you can visit historical sights but you pay ridiculous prices to get in, ridiculous prices for any kind of tour, HUGE mark up on any food or drink you want to buy there and you'll probably be in the pissing rain. It's not a relaxing experience lugging round warm sandwiches and drinks so you dont have to take out a second mortgage to have lunch there and carrying a coat just in case
A lot of the UK's "historical sites" are either free or fairly cheap - ruins, churches, towns, landscapes. Agree that NT and EH are expensive, but even some of them are good value.
It really depends where you go. Orkney, for example, is full of little ancient sites to visit, many of them free, with free talks and tours. Or you could spend £7 to visit Skara Brae, built 1000 years before the pyramids.
Or you could go to world-class museums, free, or any of a network of little local museums, some of them crap (I love these) some of them wonderful.
One of my favourites: Porchester Castle, near Portsmouth. it's a big site, one of the best-preserved northern Roman forts, with Roman stone walls 20 foot high, built to defend the shore from Saxon raids in the 3rd century. It's free to enter (unless there's an event on) and free parking. Once you are in, there's also a Norman fort - you do pay to enter this if you want to look inside. There's also inside the fort a working church, with a teashop attached. At this teashop you might pay around £2.50, tops, for tea AND homemade cake. If you want to go crazy, you could spend £2 on a jar of homemade raspberry jam to take home. I love everything about this place. And the rest of Portsmouth - if you don't want to pay to go into the dockyards, there's tons of more free places to go, and you can't cross the street without stubbing your toe on Napoleonic fortifications. The best place to buy a sausage sandwich is in a tiny Tudor castle with napoleonic fortifications (all free) where Henry VIII stood to watch the Mary Rose sink.
And, my god, Pompeii is wonderful, but you can't claim Rome isn't expensive.