The rule is 90 of the previous 180 days. So long as you have spent at least 50% of your time in the UK you are fine.

My aside is that I normally just hand my passport and they stamp it without second thought, even though many times it was several months. I was a legal resident (not currently residing in Schengen) and really never even showed my residence card, nobody even bothered. Only once was I even asked for it crossing the border.