IN A shift from the optimistic projections made at the beginning of the eighth round of the Sino-British talks on Wednesday, Britain made a low-profile departure from yesterday's meeting. Britain's chief negotiator, Sir Robin McLaren, refused to comment on the progress of the talks after four months of trying to break the deadlock on democracy reforms. The ninth round of talks is scheduled for August 16 and 17, after most of the British team members have returned from their holidays. Robert Peirce, who will take over from William Ehrman as the Hongkong Government's Political Adviser on August 23, will be absent from the next meeting. Sir Robin refused to describe the atmosphere of yesterday's meeting with Chinese officials. He would only say the British side had been involved in ''substantive discussions'' with the Chinese side following the guidelines laid down by Foreign Secretary Douglas Hurd in his earlier visit to Beijing. Asked if the talks had accelerated, he said: ''It's difficult to say whether one's running or walking. But I have certainly had a feeling that we have been engaged in serious discussion.'' Sir Robin sidestepped a question about whether the political reform proposals put forward by Governor Chris Patten remained an obstacle to the talks. He said: ''I am not talking about obstacles to the talks. I'm simply saying we have now engaged in substantive discussion. ''The object is to agree on arrangements for the 1994/95 elections which are open, fair and acceptable to the people of Hongkong.'' The Secretary for Constitutional Affairs, Michael Sze Cho-cheung, said the British side was ready to amend the political reform proposal put by Mr Patten, if necessary. Mr Sze would not confirm whether Mr Patten's proposal was one of the many being discussed on the negotiation table, but said: ''I think we are engaged in discussions of all issues connected with the 1994/95 election on which the Governor has made comprehensive proposals. Quoting Mr Patten as saying that his was only a proposal, Mr Sze said: ''I would not be surprised, at the end of the day, that there are changes to those proposals.'' He said the two governments were trying to speed up the talks, noting that several of the British team members had had their holidays cut short to make way for the talks. Meanwhile, Sir Robin also said he did not think the passage of the subsidiary legislation on combining the Yau Tsim and Mongkok District Boards would enrage the Chinese authorities. Previously, the passage of the Boundary and Election Commission Bill and a decision by the Legislative Council constitutional development panel to discuss the 1994/95 electoral arrangements had been strongly criticised for pre-empting the Sino-British talks. Mr Sze said the change was based on the population distribution and was not related to Hongkong's political reform.