Cheer up, you will only need 4 posts. If you build the whole lot out of 4x4 posts and 6x2 tops, sawn and treated, you'll get change out of £200. Easily built in a day (if there aren't blocks of concrete where the holes must go).
Is that one you did? One of the reason I am hesitant about extra posts is the rear neighbours garden is about 50cm lower and there isn't a lot reinforcing/propping up the soil at the rear so it sometimes slips down and under the fence.
Those examples do look decent though.
Cheer up, you will only need 4 posts. If you build the whole lot out of 4x4 posts and 6x2 tops, sawn and treated, you'll get change out of £200. Easily built in a day (if there aren't blocks of concrete where the holes must go).