The only bit I can help you with (I live in Harrogate) is that Harrogate Ladies' College is very well thought of, it's not academically selective, but I think the results are good. It's based (litereally) in the centre of town.
Have you considered Ashville, one of the best schools in North Yorkshire - it's a boarding school should you need it, but is co-ed (I note the other two are girls only schools). Find the ewebsite here: http://www.ashville.co.uk/
Leeds Grammar (not a grammar school but an independent) has a 'diamond' system which means the intake is mixed (boys and girls) who share common form/tutor time but go off for single sex lessons and come together again at break/lunch times. Again the standard is very high and may suit you as the best of both worlds. My one thing against Leeds Grammar is it's a big school - find the website here: http://www.leedsgrammar.com/