I'll try and break things down a little.
I would personally try and aim for a diesel model, either a 118d or 120d. Purchase price will be a little higher than the equivalent petrol car but an increased mpg figure and better residuals come resale will make up for that.
Both the 118d and 120d should average at least 45mpg on the combined cycle. Assuming you will cover 10,000 miles PA, this will equate to around £1500 a year at todays fuel prices.
Insurance? Couldn't really say to be honest. You will need to run a quote yourself using your details.
Servicing - BMW Inspection I & Inspection II depending on the mileage of the car and the previous service history. On a mileage of 10,000 PA, without any repair work being carried out, expect a bill of around £400 per year. This will obviously increase if the car needs items replacing.
Tyres - For a 1 Series on 17 inch wheels, expect to pay around £100 per corner for a decent tyre. Tyres will last around 15,000 miles before requiring replacement (obviously dependant upon how you drive).
To summarise, a base model 1 Series i.e a 118d and not a 130i will not cost much more to run than any other equivalent car.
Parts on a BMW will typically cost a little more than a Ford for comparisons sake, but nothing that will break the bank.
The crux lies in whether you buy a decent car to begin with or one with many problems.