[Tannaton]

It can be caused by weak/split front wishbone bushes.

When you brake, the wishbone moves back, in doing so it effectively shortens he track rod end on that side and pushes the wheel out, this can set up a reciprocating action with is felt on the steering wheel. So I would check your wishbones..

All the good books say don't re-use brake pads but, especially after just 5k, I would. You might want to re-face them using sandpaper on a flat surface if the old discs weren't perfectly even, and carefully bed them in to the new discs.

I would never normally recommend that but knowing you understand your car and will proceed with caution, I can't see a reason as to why not.