Sorry for the delay been on holiday
Thanks everybody for the comments, Thom Thom; example build a terrain then the clients wants me to add some steps, then next day wants them taking out and a ramp adding. I end up with a mesh with patches added and over a period of alterations it gets messy and hard to use. I notice the expert users always display clean equally proportioned meshes so either i need some training in sandbox / quads or there must be a way of re forming a mesh once i have made the alterations.
I have enclosed a screen shot of an example, this site has been regularly altered over a 12 month period.