Running costs are pretty important. Good questions to ask when looking at a car (in person) are:
How much does it cost to fill the petrol tank?
How much does the yearly tax cost?
How much does the MOT cost?
When was the last MOT and Service performed?
How much will insurance cost?
You can already answer a few of these questions by looking at the ads
I'd cross off the first and last one, because the tax is much higher.
Run an insurance check on a price comparison site for a car of your preference to see if you can realistically pay the insurance costs. Also, I know you'd rather have black, but this can actually result in higher insurance premiums due to them being harder to spot at night!
You want to go for the one with a lower millage as well, as these have had less use and more likely to last longer
Don't go for the cheapest one either; they are cheap for a reason (also, a car that's 13 years old with only a 120 miles on the clock? If that's correct the car shouldn't run! Don't go with that one!) :P
I'd personally go for either the second or forth option
The forth one is the most expensive but has cheaper tax and less miles on the clock. However if you only intend to keep it for a few months, then spending less and going with the second option will probably work well too
Hope This little essay helped