CHINESE and British officials yesterday cautioned against over-optimism about the ministerial meeting between British Foreign Secretary Douglas Hurd and his Chinese counterpart Qian Qichen. Britain's Ambassador to China, Sir Robin McLaren, tried to lower expectations of a breakthrough. ''There's still quite a lot of work to be done, that's quite clear,'' Sir Robin said. Also the chief British negotiator for the talks on the 1994/95 elections, Sir Robin said Mr Hurd would seek to set guidelines for those talks when meeting Mr Qian Qichen on Friday. Speaking after the first day of the seventh round of talks, he said Mr Hurd would stress the essentials of the territory's future constitutional development. ''He [Mr Hurd] has made clear that he is not coming to negotiate. He wants to come to perhaps lay down guidelines, to stress the essentials from our point of view.'' Mr Hurd is to arrive in Beijing on Thursday night and hold talks with Mr Qian on Friday morning before flying to Hongkong. A Chinese source was also cautious about the meeting. ''There is still a long way to go before reaching any agreement. We can only wait and see on the outcome of the talks,'' he said.