heat intolerance

i have recently been on a weeks holiday in Turkey where the temperatures where reaching 30+ daily and my mobility was fine, upon my return to the UK i spent a couple of hours in the back garden and i struggled putting one foot in front of the other. I would be interested in knowing if anybody else has experienced this, i am aware that extreme heat can make symptoms worse but am at a loss as to why i was better in higher temperatures. thanks in advance for any answers.