What are the best travel agencies/guides for two teens traveling to england, france, and italy alone? Help!!!?

Ok, I'm 18 years old and my cousin is 16. We're planning on going to Europe this summer from july to august for a month. England-about 10 days, Italy- about 10 days, and France- about 10 days (may change depending on whether we'd rather stay in one country longer). We're going to travel from one country to another by train. We've never traveled outside the U.S. by ourselves and we need a lot of help. What do you suggest we do? I dont want to go on a rigid tour, I'd rather just get a good travel agent for some guidance but I don't know where to find one. I went on tripology but they said they couldn't find one for us which I find hard to believe...I'm going to read some travel books hopefully that helps too (I've heard that the "Let's Go" series is the best for young adults) PLEASE HELP!! ANY ADVICE WOULD BE GREATLY APPRECIATED!!! =)))) thanks a lot!!

If you start to consider a tour, I'd honestly look into EF College Break.. They are cheap, and they offer alot of free time on their tours.. so it's not the normal listening to history lessons crap all day.. I personally also use EF College Break when traveling abroad. (That's if I'm not backpacking).. My experiences have been absolutely amazing,.... And the code Tech2009 now will save you money on tours with them..