Half a dozen fence posts rotten and breaking at base - cheap alternative to replacing them?

[scbk]

Are the current posts in concrete or not?

If not...... you could knock in standard square fenceposts (5ft6, £3-£5) right next to the existing posts, and screw the two together using decent screws (or bolts)
Should last 10years

 

[Rollerball]

Thanks. Nope, not in concrete.

 

[oldbutnotdead]

If your fence borders a highway you've got a fair sized potential liability if it falls over and hits someone/something or causes an incident.
I've never encountered galvanised metposts but pulled plenty of failed painted ones out.
One budget solution that's done me quite well is scaff tube set in concrete but not embedded- used some 50mm internal dia plastic tube in the concrete then just drop the post in. Gravity is your friend, if it rots or bends then unbolt panels, lift tube, replace.