Hello again,
I also
don't understand why I need a fiancee visa in order to get
married- can't we just get hitched in London when I show
up on an automatic 6 month tourist visa generally granted
to Americans?
Actually, no, you can't really do that legally. When you come to the UK, they will ask you about the purpose of your visit at immigration. If you tell them you are visiting then you will be expected to do just that...and then leave without having taken any employment or overstayed. You'll have to have funds to prove you can support yourself for the entire length of your stay, and they can and will search your belongings for anything that might prove you have other plans if they suspect you aren't being truthful.
You may also be asked to prove that you are returning at an appropriate date within the 6 months the visa allows. If you arrive on a tourist visa and get married, you will have to prove that when you came over, you had no intention of doing that. And that isn't an easy thing to prove.
It seems to me that coming over here on false pretenses (ie, on a visitor visa when you clearly are planning on staying and working here) is a very bad idea and could end up in deportation. Trust me....don't mess with immigration. There are lots of people here who had stronger cases for living here who have gotten turned away for the slightest suspicion of not following the rules. It happens more than you might imagine.
I'd think the easiest thing for you both is to get married in the US, and then let him apply for your spouse of a student visa from the UK once he's here. I'm sure whoever is working with him through this PhD programme can help with this. I'm quite confident that you won't be able to come and be with him here in the UK unless you are married first.
I'm not trying to scare you but I'd highly recommend talking to someone at the Home Office about your particular situation since it is a bit unusual.