Moving from Los Angeles to Hertfordshire and thinking about a £500 car

We are moving to Hertfordshire in October for 10 months. In looking for house rentals we have found some great places but many of them are 2 miles or so to the nearest train or school (my son is 8 years old) I was thinking about buying an inexpensive used car and then selling it before we return to the states. Advice? How expensive is insurance and MOT and all that? I have a clean driving record in the U.S. but does that figure into things? I am open to suggestions. Also, do I need a UK license? So many questions! Are there any makes to totally avoid? Any input is greatly appreciated.

I don't drive, but I hear the breakdown coverage is pretty good here. So if you go for a "banger", it might be a good idea to join AAA or something.

Insurance will be your biggest hurdle, as it's hard to be treated as an experienced driver when you have no UK license or history.  You'll be lucky to get a policy around £600 a year.  It could easily be over £1000 for a year without a UK license (which you won't have time to do if you are only here for 10 months).  MOT's are cheap, usually less than £50.  But if the car needs work, then it could be expensive to get it to pass.