two different brickies might give you two completely different prices, depending on whether or not they needed the job, how busy they are etc.
as for the height i would say that you choose a height that you want and then the wall is constructed in size/width to suit that , either by rule of thumb or getting design help from an engineer or architect or asking the brickie.
would,nt your local building regs/planners expect some sort of design with calculations?
I didn't bother answering this one, Terence, because it is far too woolly.
Commons bricks are cheap as chips, decent bricks are twice the price.
The thing needs piers to be constructed because of the length.
The thing also needs a dcent foundation which will gobble up probably 20% of the overall cost - but very much depends on the subsoil.
Maximum height for a new wall/ fence fronting a highway is 1.2 metres. Maximum height for a rear garden boundary wall/ fence is 1.8 metres. Higher than either will require planning permission. If you build something that needs planning permission but the local council don't notice for at least 4 years....and it's up to you to prove the four years...the structure becomes Lawful Development and is immune from planning dept. prosecution.
Seafarer where did you get your figures from??? Its 1m for a wall adjacent to a vehicular highway or 2m elsewhere. Any higher than this requires planning permission