I just saw your other post about being an MSc student, currently in the UK and staying here for a job - I'm assuming you have been studying in the UK on a Tier 4 visa?
Are you aware that your US licence was only legal for you to drive on for the first 12 months of living here? The 12 months started the date you moved here on a student visa.
This means that if you have been here for more than 12 months, you are no longer legally allowed to drive here on your US licence... so, you will need to take and pass all the UK driving tests before you will be able to drive on your own.
As it stands, if more than 12 months have passed since you moved here, until you have a full UK licence, you will need a UK provisional licence to be allowed to drive in the UK... and you will be treated as a learner driver... which means:
- you MUST be accompanied in that car AT ALL TIMES by someone over the age of 21, who has held a full UK licence for at least 3 years
- you MUST display red 'L' learner plates on your car at all times
- you are not legally allowed to drive on motorways
It can take up to a few months to pass the UK tests and you may well need to take a few driving lessons to learn how to pass the practical test (as it is very specific and generally less than 50% pass on the first try).
In terms of insurance, if you've been here more than 12 months, I doubt you will be able to get insurance for your US licence, as you are not legally allowed to drive on it.
If you haven't been here for 12 months yet, you can still drive on your US licence until the 12 months have passed (so you will need to get your UK licence before that happens if you don't want to be treated as a learner), but as you have no UK driving history, you are likely to find that insurance is still expensive - probably over £1,000 a year. They may take into account your US driving history though.
If you have been here more than 12 months, you should be able to get insurance as a learner driver on a provisional UK licence, but as you will be treated as a learner, it will likely be very expensive - probably between £1,000 and £2,000 per year.