I'm sure I'll be repeating the wonderful Peedal...but for what it's worth:
1) Assuming we get married in the US what right's does this give me without applying for a Spousal Visa first?
You can't apply for a spousal visa even if you are married in the US. If you get married in the US on a visa waiver, you will need to come back to the UK and apply for a settlement visa (see the repat board for more on that process) Basically, you'll be separated until the visa is approved because you won't be allowed to even visit the US while it is being processed. She will have to prove she can support you, etc.
2) If we are given a Spousal Visa does this allow me to come and go between the UK and the US also including my Fiancee and her kids?
I think you may be slightly confused about what a spousal visa is. The spousal visa allows your American spouse (it is her visa...not "yours" combined) enter and settle in the UK with you. She and her dependents can come and go as she pleases as long as she doesn't exceed the amount of time allowed her to be out of the country. It doesn't give you any additional rights in the US at all.
3) If I had to stay in the US for a while after I was married would I be able to work in the US with or without the Spousal Visa?
Nope. No way, no how. Not legally anyway. Again, the spousal visa doesn't give you any additional rights than you already have in the US as a foreign visitor.
4) I'm assuming if we want to live in the UK for a few years we would apply for the British Spousal Visa at the Brtish Embassy in Los Angeles (This is the closest to her) and if we wanted to live in the US then I would need to apply for the US Spousal Visa?
Again, it's the consulate you need to get a visa from for her to come to the US, not an Embassy. But the LA one is likely where you'll need to go. If you want to live in the US after you are married, you will need to go through US immigration *before* you go to the US, unless you want to get married and then be apart while you wait for the visa to go through.
It's very simple. If you want to live in the US, YOU have to get a settlement visa. (Check out the repat board for advise on this process.)
If she wants to join you in the UK and live here, SHE has to get a spousal visa.
Getting her to the UK so you can live together is a much easier, quicker process, which is why most people do it this way rather than for the UK person to go to the US.
5) Let's assume we are married (in the US) and a Spousal Visa is awarded. We move to the UK, does this allow Jennifer to work as she pleases in the UK? When or would she be given her UK National Insurance Number? Would she be entitled to the British Public Funds if we had too?
If you get married and Jennifer gets a spousal visa and you come to the UK, she will be able to work immediately. She'll need to apply for her NI number when she starts looking for work and will need to go for an interview for this. (There is some discrepency with the Benefits Agency on this one....some people have found they won't give NI numbers until you have a job, but the official policy is that you need only to be looking for a job.)
She would *NOT* be entitled to public funds.
It is all very confusing when you start down this path but keep reading and finding out as much as you can. It will be fine if you just take your time and go by the rules....no matter what country you decide to start out in.
