I visited about 2 years ago, and the whole charm of the place was the best tour I've ever had anywhere from someone who truly had passion for the place. We got the whole story, in a perfect setting. Sure the huts need a little TLC, but a glitzy visitors centre is not what is wanted here.
The computing museum, helped to bring the story of the past up to date and was just as interesting as the main Bletchley tour. Also the Churchill museum was an integral part of the story, I understand that's now been removed. The toy museum, although cramped was just as interesting in transporting me back in time.
I would hate to see a sanitised version, cleaned up for the modern age, with tour guides who are no more than just workers doing a job. It's the guides who really made the day, people like that with memories of how it was won't be around for ever and the trust would be well advised to keep them as long as possible. The trust wouldn't exist if it wasn't for those guides keeping the place alive.
I half expect a gift shop with tea-towels and jam is probably on the agenda as well!