When the wife and I went to England and Scotland two years ago , the flight cost us $5000.00 and we spent about $250 a day on accomadations, food and drink. Car rental was another $200 Not counting gifts that we bought to bring home the total cost of the trip for 10 days was over $8000. Not cheap by any means.
Not challenging a sing word of the above. Summing up, however, a recent trip I took to England (going again in May):
Airfare per person: $1,400. I won't say from what city. I just checked the same airline using the same dates and found Newark/London round trip totals $1010 per person with tax and fees included, 2 bags free, no extra charge for seat selection.
Hotel, European style within walking distance of two railroad stations in London, $105 for two, including full English breakfast per night. It's basic. Old but clean and very convenient to three underground stations.
Transport airport to hotel: Approximately $10/person using "tube".
Meals, (Breakfast included with room, no extra cost) light lunch in local bakery or deli, substantial evening meal in nearby pub, total about $30 per person per day.
Stonehenge day tour, includes bus and admissions, about $145 per person.
I do not recommend car rental from London. If you must drive then ride the tube out to Finchley and rent from a local outfit at about 1/2 the cost of a London rental. For tube travel, get a "visitor's Oyster Card" which is a pre-paid card with an upper limit on what gets charged during any one day. For days when you want to do a lot of sightseeing in or near London, it's dirt cheap. If going to some place like York and wanting to drive the countryside take a train to the hub city and rent there. If doing extensive rail travel get a railcard - several varieties available. Senior railcard typically saves 40% off each fare. I've done London/York for as little as $19 by buying 12 weeks before travel when the "on the day" fare is over $120. It works out to about $110/per person per day including eating well and a lot of in-town tube/bus travel.
Most museums and attractions in London are FREE. Many attractions away from London are either privately owned or run by English Heritage or National Trust and do charge admissions but there are lots of museums and public parks that are free.
OK, I don't do a lot of travel to other countries in Europe anymore and the little I do has proven expensive but I don't have the experience and knowledge of how to do it on a budget. But.....if you put your back into it and spend enough time researching online you'll be able to pull together continental travels for the same kind of money I outlined.