groom said:
My questions are
a)what is the legal status of this structure. A friend told me that it has been around long enough (> 7 years) to be legal? I don't know what basis he has for that. Can it be bought/sold/rented?
There are 2 possibilities - either it is an exempted development (if it is less than 25 sq.m., your mother has more than 25 sq.m. of yard left over, there are no other sheds, garages etc. which take up some of this 25 sq.m. etc.)
or it is not (if it does not fall STRICTLY within the above exemption)
Even if it is not an exempted development, it has been built more than 7 years ago, which means that the Local Authority has lost the right to tell you to knock it down.
It would be difficult to get a mortgage for it etc. however, because as an unauthorised development it is subject to certain restrictions - e.g. if it burns down, you have no automatic right to rebuild it.
groom said:
b)if I were to buy it, it would not have direct access the main road. Could I get right of way written into a contract.
Yes.
groom said:
Which authority does one consult on these matters - the local counsil?
Firstly speak to Architect/Engineer about whether your structure is exempt.
PLEASE NOTE: You DO NOT have the right to turn the shed into living accommodation - this is a change of use. To give an anology, you cannot turn your own house into a nuclear waste reprocessing plant "because I got permission for a house".
You will require planning permission for this.
Your chances of getting this are quite likely to be in the vicinity of "slim to none" (this is without looking at the plot though - if it is quite large, you might be able).