Thaks for the advice guys.
I had mine done on the C5 and was under the impression that they were the same on a 407.
The guy at work with the Berlingo assures me that this is not so and that the 407 has the joints welded into the arms and the whole arm has to be changed and this allegedly involves removing the McPherson strut among other things.
He has a mate with a 407 who has recently had this done and has been told that it is a common fault with high mileage vehicles - the one in question is a 54 plate and has 120,000+ on the clock.
He did get another quote during the day ond it was £240, a bit better but not much.
I paid next to nothing for mine - I already had the ball joints, my son in law did one side with great difficulty, I had the other done when the car was serviced and I don't think he even bothered to charge for it.
It surprises me that there should be such a difference between the two cars. I have to admit to a fair amount of scepticism here.
Ed: title and posts - silly me put 307 and it should have been 407 