Jono wrote:My car only has audible knocking noises when going slow... over small bumps..
Well it seems an easy thing to check. Sit in your car whilst it's off and just swing the steering wheel from side to side. If you hear/feel a knock, then get your mechanic to check out the steering rack and associated bushes and links.
As for knocking over small bumps. I get distinct noises from both the front and rear. I will be replacing all sway bar links, I have second-hand ones for the front but looks like I'm going to have to get new ones for the rear. Your problem could be something that simple or it could be the struts. Or perhaps something totally different.
If you want to check your sway bar links/drop links, pull them off and play with them

They should be a stiff, tight fit when you try to rotate them. Push and pull the joint too, there should be no movement in and out, if there is, they're stuffed and need replacement. They will be causing a knocking noise if there is movement in the joint.
All I can advise is get several opinions and steer clear of "franchise" mobs. Look for one shop businesses that _need_ to make sure you're happy because if they stuff you around, they do themselves out of a customer and risk getting a bad name. Try and get the mechanic to go for a drive with you so you can point out exactly what you are talking about too.