Estate agent's mortgage advisor

I am starting viewings to buy a property and I have agreed with one estate agent that I will see their advisor to discuss mortgages (I think he said they can give me an agreement in principle). But as soon as I got off the phone I wondered if this was a mistake - if the estate agent knows how much I can afford, bargaining may be more difficult. Or are their supposed to be "Chinese walls" between the sales negotiator and mortgage broker?

Should I go to the appointment, but only for a discussion, and not give any information? Or be careful about what I say?

Or should I cancel it?