Chanster,
If you are not used to working at these heights and using access equipment, you NEED to speak to someone before you even think about looking at the job or you could end up getting in to something which could cost you and create all kinds of problems.
It is not the height you need to be worrying about it is the H&S which you will have to sort out and also the positioning of the building, ie: road closure, traffic management systems, noise etc
If you want to give me a ring i will do my best to give you information as to what way to go and possibly give you an idea of pricing something like that
Thanks