So it was fine before the work...And it gave the exact same symptoms over two different sets of wishbones?
I'd be pulling the wheels off and check everything is tight including the wishbone ball joint clamp clamp on the stub axle (100nm) and that the rearward bush hasn't failed already.
I can't see drop links causing this, they work to control body roll.
...."sounds" like a less serious case of lower control arms (wishbones) failing to control the position of the front wheels, due to failed rear bush or loose bolts. But this is usually accompanied by the steering wheel pushing the opposite way to the pull.
If the steering wheel is following the pull normally, it may just be set up. But we can't tell how severe it is through a keyboard.
Any more than that is difficult to say. As TB says given your just up the road from wheels in motion in Chesham it might be worth a chat with Tony Bones and get them to look into it after you've double checked everything, but before setup (includes castor, camber and toe on the front, and camber/toe on the rear)
I'm not sure how Wim would charge if they found a fault needing repair first. So worth a phone call. mention oof and it's £60+vat iirc. Trouble is, spending that sort of money you need to be confident that's going to fix it.
It would be most annoying for the fault to remain.