@Paul ******
stayed 29 days across February to March, stayed 7 weeks across end of July to early September, then 4 weeks end of November into December last year, didn’t have an issue.
It is definitely at the sole discretion of the I.O you encounter at the arrivals hall wherever you enter, but as others have mentioned, the I.O’s can see when you are keeping tourist movements as opposed to those the try to abuse the visa exempt system.