Harry Potter Warner Bros.Studio Tour--self-guided or group tour?

I've been to the Studios under my own steam. I can't imagine that there are guided tours but if there are they wouldn't be very satisfying because there's so much to see that you really want the freedom to go at your own pace. i think the only advantage of a tour might be that they secure tickets in advance that might be sold out if you don't prebookmseveral months in advance. You enter the tour in a group of about 150 and all watch a short film together, then a guide takes you into the Great Hall, says a few words and then off you go into the main exhibits. Obviously these are film sets so you'll get most out of it having seen them.

The only change is that the gang running the trains has changed so it is no longer London Midland (sad) and is now London Northwestern.

Same trains, same staff, same stopping patterns, virtually the same departure times, same running times. Different uniforms. Different paint (well, vinyl) on the trains.

I found the digital guide very useful and informative. It explains the concepts/ideas/background of what you are looking at.

I agree that travelling to and from Watford on your own is the way to go. Very easy to do, and you can use your Oyster card to pay for it. The tour companies are only providing tickets and transportation; a convenience that comes with a hefty markup in price. This, however, may be your only recourse if tickets have already sold out for the time you will be in London.

We bought neither the digital guide nor the souvenir book ; we just used the map/guide that is provided to everyone entering.

I'm not sure how complicated the train is from Euston Station to Watford Junction but I have friends (who travel abroad frequently/mom is a travel agent). Apparently, they took a slow train by accident and Warner Bros turned out to be a looong all-day affair. I've read online Warner Bros Tours are supposed to be:

1 hour total travel time (including tube to Euston Station, train to Watford Junction, shuttle to Warner Bros)
3 1/2-4 hours at Studio
1 hour travel time back

I also have read that the Midland trains are 5.50 off-peak and 8.80 peak travel each way. You can just tap in and out with your Oyster Card.

Last, there is a Euston Square station and a Euston Station. The train to Watford Junction leaves from Euston Station, which is a train station. I didn't realize there are two different train services (Virgin and Midland) that go to Watford Junction.

The train on one's own is very easy, and the digital guide is wonderful. At every exhibit there are videos about how things are created. The hardest part for me was slowing down my 10yo traveling companion so I had time to watch some of the videos. And I'm his grandmother and went knowing almost nothing about HP. Loved it!

Don't get on a Virgin. They do not provide service between Watford Junction and Euston. The northbound at Watford Junction is for boarding passengers only, not for setting down. The southbound is for setting down only, not boarding. The doors will be closed as soon as the proper procedure is complete regardless if people are trying the one not approved.

Also, no ticket valid between Watford Junction and Euston is valid on Virgin trains - leaving you open to a large fine.

Just take the London Northwestern Rwy ones listed above and don't worry.

I just wanted to mention that there will be no trains from Euston Station over Easter Weekend if that happened to be the time you were thinking of going.

Thanks all for the helpful replies. Nigel, your advice and insights are indispensible. CaliMom--thanks for the overview of timing. I think we are in good shape for planning this as we won't be going until mid-August. Cheers!