Click the "Buy A Railpass" in the toolbar above. Once you’ve done so click "help me pick a pass." From there fill in your itinerary and it will help you chose which pass is right for you. Don’t count on getting too much sleep on a night train. Getting a couchette will help. On my last overnight ride, I popped a couple of Tyenol PM’s and was out like a light.

When using railsaver.com from the "buy a railpass" link at the top of the page, it doesn’t immediately give you the "use a railpass only if it saves money" option. Click on "more destinations" (even if you don’t have more)for that option.

For rough budgeting: plane ticket + city to city transportation (in your case I’d figure a 3 day Britrail pass plus a 21 day Eurail pass — you probably won’t buy those passes, but it will give you a good idea of the total you’ll spend on trains, buses and planes between cities) + 50 euros a day for hostel, food, adminission fees and local transportation + 200 euros emergency funds. While that includes some beer it does not include a lot of money for partying in the expensive cities you’ve picked.