Choosing not to answer does not imply guilt, however simply stone walling with "no comment" is probably not as good an idea as it would be in the US (although a solicitor would be able to advise you on what you should answer).
I'm not sure whether "questioned" just means when you are at the police station or also during the time of the arrest. I would assume it could refer to both "why did you not bring this to the attention of the officer at the time of the arrest?".
Although I would imagine a rational jury would think that waiting for legal advice was a sensible thing to do.
Regards duty solicitors, I always thought that these were really private solicitors who were put on a rotation and were strictly kept separate from the police?
http://www.jfhlaw.co.uk/faqs/crime-faqs/what-is-a-duty-solic...
If there is a case of corruption here then that would be extremely worrying as the people most likely to be charged with crimes are also the people with the least ability to pay a private solicitor. Is there anything to back this up?
I'm also not sure I would want a solicitor who "hates" the police, I would want somebody motivated to help me, not get one over on someone else. The adversarial relationship between the police and solicitor should be professional and not personal.