I don't have to much advise for you but seems our situations are very very similar. I'm planning to make the move soon as well & commute bk to London 2 weeks a month for work (mainly as I don't want to be tax resident in spain) same as you I like Marbella/Mijas area as im young, early 30's and want a bit of life and atmosphere with mix of Spanish and English. I've been to the east of malaga - nerja, frigliana etc its beautiful but for me its way to quiet & is mainly retired people. Marbella/calahonda type way seems to tick all boxes but a good 60 mins from airport and more expensive. From experience I would rather an extra 20min commute to be in an area that meets your requirements than to live somewhere close that doesn't, just food for thought especially as fitting in to a new culture is going to be vital.
Maybe can meet for a beer over there, i'm in Marbella area for a month in September.