Thanks folks, all sounds good, as you say you don't want to be digging them out because you rushed putting the gates on, I do it for a living so i have to make sure it is right & don't want to be going back to repair it, It's the ground around the hole that will hold the concrete & post up so you have to take that into account & try not to disturb it too much
Decking can be no more than 50% of the garden & no more than 1ft above ground level but as long as you don't get any complaints within 5yrs the authorities will find it hard to make you alter it,
I don't often concrete the decking posts in, i make the framework & legs solid so if it was just standing on its own it would stand like a big table. i dig to solid substrate then sledge hammer the legs in the compact it further. & put more than legs than i think it needs.
If the ground is still soft 2ft or so down i put a concrete foot pad for the leg to stand on,about 1ft thick & 18" round to stop it sinking,
Just be respectable to the neighbours privacy,tell them what you have planned & there shouldn't be a problem
Happy building people, it's a nice feeling when you've done.