Is it a safe purchase? We Buy Cars or DEKRA "A" rate?

We very recently bought a DEKRA A rated vehicle from We Buy Cars, East London. Everything appeared to be A okay with the vehicle, it was in any event an A rated vehicle. That, with a bit of "trust" made us feel quite safe with the purchase. The client service on securing the deal was good, especially from Khan and the Pestana couple, until all the paperwork was (almost done) and dusted. The final sign off was to indicate the condition in which the vehicle was received, when it was noted that the windscreen had quite a number of serious stone chips, some bigger than others. The glass expert who was coincidentally on the premises indicated that a maximum of 3 chips could be fixed, but more than that would quite possibly exceed the price of a new windscreen. We then approached the Sales Manager, a fairly young man, D, who immediately acknowledged the chips. Said that he'd check with the regional manager about having the windscreen replaced. A few minutes later the Sales Manager conveyed a message that the windscreen could only be restored if there was visible damage. I could not believe my ears... that such a major dealership would take that stance. He, D, was adamant that the vehicle passed the roadworthy test and that we should accept it at that - so it was an acceptable standard for We Buy Cars, that we could drive off with the car in that unsafe condition. This was clearly unacceptable. Was the problem with We Buy Cars assessment and conditions of sale or was it that DEKRA rated the vehicle as an A class?? How did it pass the roadworthy test?? Please tell me... Later-on that evening we took the car for a drive and discovered that the switch for BRIGHT LIGHTS does not work. We had to cancel the night driving lest we could be faced with a compromising situation that could potentially have been unsafe. Again, how did the vehicle pass the roadworthy test or be DEKRA A rated?? What are we to do about this good deal that clearly ended up souring the trust that we had in a We Buy Cars deal. You might just advise against buying cars from this dealership in future?

Please assist.