Hi thank you for your question, my name is Steve and I am a fully qualified technician with over 30 year experience in the trade. Hopefully I can help you.
I am presuming that other than the problem with the inertia switch your Audi was driving fine and you had no other problems.
You also mention that no warning lights were on.
The two sets of problems are being presented as two problems but they may be related, and the decision is really do you have a problem?
It would be good to know the codes read off by the garage, and I can tell you from experience that there are many cars driving around with fault codes logged in the system without detrimental effect.
I would advise that you find a garage who will clear the codes, and possibly re-check them in a weeks time, historic codes in the ECU can be flagged up during certain driving conditions, but once cleared may stay away.
It would in my mind be unadvisable to have so much work carried out on the strength of the codes in the system, when no faults are present.
Does the ABS ever judder or come on during normal braking and does the gearbox ever not change smoothly?
If the answer to both these questions is no, then I would not spend out on the repairs listed.
I hope this answers your question but do please feel free to contact me for any further information.
If this does answer your question please click accept and rate me, this will allow me to continue.
I can answer any further questions even after you have clicked accept.