Are these a pain to fit?

[Piggy]

Or out of simplicity, replace the wishbone as most already have p bushes attached.

"wacking" a new one on, i guess you mean weld if it involves chopping?

no...

chop the old bush off...you just use a hacksaw or thin grinder blade and run it diagnoally across the old bush and through the inner sleeve...trying not to touch the wishbone itself.
the p bush should then just tap off/fall off.

then line up the new p bush and with a press...or lump of wood, socket the size of the inner sleeve and a hammer...wack on the new one!