There are many stonehenge-like places in britain and ireland. Most of them are a maybe a bit less well-preserved or somewhat smaller, but they also don´t atract as many tourists. Avebury is one of those places.
I think that, if you´re going to the lake district, there´s a chance that you won´t feel the need to travel any further and see more, as it´s a very, very beautiful region and the only thing that could maybe spoil it for you is the wheather. In the northwest of europe, summers tend to be either very sunny, or very rainy, or you´ll just have twenty different types of wheather a day.
London and edinburgh are britains most cultural city´s by far. London is a metropolis where you can find anything a person can be into. If you stay there for three days, you´ll notice that your snot has turned black from all the airpollution, but that´s what you get in a modern metropolis with way over ten million people. London has some nice village-neighbourhoods that will make you forget that you´re in one of the biggest city´s on earth and london is situated in a valey. Meaning that there are many places in london, where you can have a beautiful view of the city. There´s one large park in the north of london, and you can virtually see all of london from that place.
The london area is fantastic. There are many very beautiful historic places round london, in the south-east region, where you can feel peacefull queitness as if the frantic metropolis is a million miles away. I personny like the place of oxford, though it is very poshy and chic. Oxford is realy a nice and beautiful place. It´s a small village, with beautiful old buildings surrounded by beautiful nature. If you go to spent some time in london, then i would realy sugest visiting oxford, canterburry and other nearby towns. Thos places, is where you will realy feel being into contact with more than a thousand years of history.
York is also a nice place. It doesn´t have a party scene or a very interesting nightlife, i think. The history you can encounter in some places...it can change your view on everything in live.
Edinburgh is always a little colder than places with a less nordic location. But it can get pleasantly warm there as well. Edinburg is probably the most beautiful town in the uk. Some scots call it vainglorious. but it is a nice plce with nice people.
The only real advice i can give you is: don´t drink too much alcohol. And never look at people who have drunk too much.
You will run into some very old things. You can take ride with a really old steamtrain that has been working for more than a century, or take a boattrip. When the weather is great, you are definately going to enjoy your stay there.
Blackpool is the englishc version of las vegas. It´s an absolute funtown. I would not want to live in blackpool, but staying there for a night or so , can definately be very fun.
I would say: London, oxford, avebury, canterbury, edinburg, lake distric. Quiet a list.