Well I'm an idiot - the fulltext index on page_text was missing from a default installation. It didn't break searches but probably slowed them down tremendously. Also set engine to MyISAM on page_text to avoid cryptic error messages from MySQL.
// UK lang variables
tinyMCE.addToLang('',{
insertdate_def_fmt : '%Y-%m-%d',
inserttime_def_fmt : '%H:%M:%S',
insertdate_desc : 'Insert date',
inserttime_desc : 'Insert time',
inserttime_months_long : new Array("January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"),
inserttime_months_short : new Array("Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"),
inserttime_day_long : new Array("Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday", "Sunday"),
inserttime_day_short : new Array("Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun")
});