Bit of a strange one, when I start my focus after about 30 seconds there is a loud thud noise, not sure if it's from the steering or brakes.

I do get intermittent vibration from the steering wheel at different speeds but not all the time.

Had 4 new tyres but was doing this before tyre change.

Thud noise is a little unnerving, if your experiencing any issues with steering, and even if you suspect it or the brakes, unless you know what your looking for you should get the car looked at properly. Vibration, potential thud, could all be issues with the rack and pinion, the PAS linkage, and overall will affect the cars handling, making it (by the policemans judgement) an unsafe vehicle. if its thudding before you move you need to get it checked.

If you get this thud after you start moving off, approximately 15mph, the ABS system can do a self test (apparently this is normal) and so you may not have anything to worry about.

In the long run, it could be a number of things, bushings, bearings, linkage arms, PAS, rack and pinion joint. Without any sort of direction (perhaps a DTC Code) there isnt really a judgement we can make to advise where to start.

If you get this thud after you start moving off, approximately 15mph, the ABS system can do a self test (apparently this is normal) and so you may not have anything to worry about.

I get the same clunk at 15mph as jeebowhite mentions It definitely feels like the ABS, it's more noticeable when it happens when the steering is turned significantly. If you're driving in a straight line, it's just a slight noise and small vibration.

It only happens once after starting the car. IE: doesn't happen if you stop, keep the engine running, then set off again.