Hi,
New to the forum so please forgive any mistakes.

I have a C180 (W203) Automatic Unleaded 2002 Saloon (UK so right hand drive). Last year during the annual MOT inspection (to ensure the car is legal to drive on the roads) the car failed due to the ABS light (and ABS/BAS/ESP Visit Workshop message on the LCD screen). The same mechanic doing the MOT (Kwik- Fit, chain of tyre and service specialists in the UK) performed a diagnostic and determined that the rear passenger side ABS wheel sensor had failed. This was replaced, the warning light and messages disappeared and the car passed the MOT inspection.
Almost 7 months later the warning light and messages re-appeared. So, as it was still under guarantee, I took it back to Kwik-Fit to see if the sensor they replaced was at fault or another (was happy to pay for a new one if it wasn't the one replaced the previous year).
However, after using a diagnostic machine, the mechanic said that not only the one they replaced was flagging an error, the sensors on the other wheels were doing the same as were other readings ( e.g.from gearbox). So after consulting with others he stated that the ABS 'Module' was at fault and would need replacing. The quote for replacement was £1300, ouch!!
So after reading a lot of info/posts on this forum would like to ask a few questions, so as to take the best course of action.

1) Is it common to determine the ABS module is at fault after seeing numerous wheel sensor errors. Would you not see single error saying the ABS module is not responsive or in error? (Would it be better to take it to the dealer to get a diagnostic).
2) After reading many posts on the forum one simple/cheap fix suggested that may help, would be to replace the brake light switch. However I've had a look under steering wheel by the pedals (removing the panels and checking where the top of the brake pedal lever arm ends) and I can't see the brake light switch. Do all models have such a switch ? If so am I looking in the wrong place.
3) I've seen posts and videos of how to replace the ABS module (note the pump was not giving any errors). So its probably something I could do, however would it be case of simply replacing the unit or would I need to take it the dealer to have it connected to their machines for it to be reset/reprogrammed/re-coded? ( the part number for the Module currently attached is A2095450232, with 3 bolts....sounds like there is a difference between the older 4 bolt units compared to the later 3 bolt ones). From the posts read so far I've seen replacing like for like (i.e. same part number) may be just a simple swap and go.

Would be grateful for any advice, pointers or suggestions.

Some extra info:
1) The errors come up as soon as I start the engine.
2) Battery was changed last year so is fairly new.
3) I've checked all the fuses related to the ABS, ESP. They are fine, have also removed and re-insterted them.
4) Mileage is 96,000 miles approx
5) Tried the sync method of turning the steering wheel full left and then right lock several times, without luck.
6) The car drives ok with the errors, it doesn't go into limp mode