There are a number of firms who have people specialising in this area, myself included.
It is certainly possible to have cases either dropped by the prosecution or successfully defended at trial. However, the only way to advise regarding this point with any clarity is to discuss the case in some detail. I am aware of some firms who will guarantee that they can find a defence, which I am always sceptical of as each case needs to be assessed on it's own facts.
I would certainly not describe Geoffrey Millers as a scam, nor any other reputable firm who deal with this area. It is a question of whether you are willing to fund the case to explore the possibility of a technical error being made by the police during the intoxilyzer procedure.
If this is something that you are interested in discussing further you are welcome to contact my department on 0333 999 7158.
If you plead guilty to the offence then you would be facing a mandatory disqualification which would be between 12 and 16 months.