You might find that the owner at the end of the road is responsible for the boundary wall and gate and all other properties only have rights of access. This would mean that technically the owner at the end is responsible for its upkeep ( hence why he has put a gate there) but I have seen title deeds where all the houses that have access are required to maintain the alley and the house on the end is only responsible for providfing a secure access point. Usually the council has no reponsibility to keep access ways in repair, this is not a footpath and is not 'open to the public' it is for only the householders use and therefore would normally fall outside their jurisdiction.
The first place to look is at a copy of your title deeds, if you have a mortgage these will be lodged with your lender. Most charge around �7 per page of copy so you have to be specific about what you are looking for as it will be on more than one page, there is usually a plan drawing of your boundraries, with a note on the covenants on the property ( thou shalt not keep farm animals etc etc) and this should have details of the boundaries and rights of access. Please do not be surprised if the copies cost about �30 as dependant on the age of your property will depend on how many documents there are ( rule of thumb, the younger the cheaper as less covenants to wade through).
If you are all responsible for the upkeep of the alley you would need to cost things out per house and get everyones approval .... and this is usually hard, someone always says they wont.
As for being allowed to buy it .... I can't see this being allowed as you would be still required to provide access for everyone and then you would be responsible for its upkeep and could be sued for any accidents if it is found to be 'unfit' . So definately would not recommend it, it would also put off prospective buyers as they would not want to be saddled with the cost or problems that it