Hi Claire, I don't live in a high rise flat, but I would imagine that the biggest problem would be the lack of a garden, the grounds of high rise flats are more often than not, the responsibility of either the local authority, or the land lord, although some residents of ground floor flats are sometimes allowed to have a section of garden, but the majority tend to be grassed anyway, Derek.

the height

If they have a verandah then the wind.

An allotment is one way of having a garden Clare.

Send a PM to Balcony - he lives in a flat and has an allotment.

any problems refering to balconies

Check if the building has any clauses/conditions re use of balcony and if there are any bylaws regarding what you can use it for?
Also check if the balcony is strong enough for the weight of compost, pots and plants which can be considerable and drainage has to be considered.
Which way it faces might impact on what will grow too.