Hi lonedad:
I can understand your obvious concern because there is a significant difference in driving deemed to be careless and that deemed to be dangerous. The main one being that you, at Crown Court, could be imprisoned on conviction for dangerous (up to 2 years, plus licence endorsement, probably 12 month endorsement, plus to remain disqualified until further driving test taken and passed.) but not for careless.
I would hope that your Solicitor has explained all the ramifications to you by now? Perhaps s/he has and that's why you were advised to plead not guilty.
Would I be right in thinking that the prosecution has witnesses to your alleged dangerous driving? I'm not talking about who you hit, but other motorists/drivers not actually involved in the collision? If so, it could be their evidence which has persuaded/compelled the prosecution to have you charged with dangerous, as opposed to careless, driving.
Believe it or not, it doesn't take much to raise the bar, so to speak, from careless to dangerous driving. There are many factors to be considered and I couldn't begin to guess how to advise you further without knowing the full facts.
What I would say is this: your Solicitor is there to represent, advise and defend you, and if they have recommended that you plead not guilty, they are presumably doing so from the point of view that they are privy to the available evidence. It would be an incompetent one who did so on mere whim. And don't forget to insist on speaking to your defence Barrister prior to entering the courtroom. It could prove invaluable to you and his/her advice should definitely be heeded.
Good luck.