You are clearly using a sub-standard replacement.
Either go OEM, or get the manufactures original.
Yes, it may cost more but...
1 X P-Bush (£22.50)
1 1/2 Labour (£45)
or you can go for Poly Bushes, e-bay have plentifull supply, but I would just go for manufacture.
They lasted until now, and you've been throuigh 3 since...
Gilkes.306
December 2009