applying for LPR status either here or there - how long does it take?? or do I measure my piece of string??
Thank you, oh wise AUK people!
IME, applying for a green card is MUCH faster if you are able to do it while still in the UK, since your application is handled by the embassy instead of the INS (or whatever they're called now). Of course "fast" in this case means 3-6 months instead of 1-2 years (or more). If you do apply from the UK, be aware that you may not be able to travel to the US while your application is pending.
It's true that once you get LPR status it's usually good for 10 years, assuming you've been married more than 2 years. However, things can get very tricky if you leave and want to maintain your status. To be (reasonably) safe you need to return every 6 months, but even this isn't always enough.
You'll find a lot of good stuff in the US marriage-based visa forum here:
http://britishexpats.com/forum/Overall the process is a monumental PITA - are you sure you really want to go?
does it make things like driving, health care, impossibly difficult?
Check with your destination state's DMV to see how long you can drive on a foreign license. My wife was able to get a license with no problem, but I think she needed to supply a SSN to get it.