I would say no chance. Baggage will not be checked through on separate tickets so you will need to collect and recheck. Baggage for long haul flights closes 1 hour before departure so you would have 5 mins! I would allow about 40 mins for baggage at Gatwick (unless it has significantly improved)
I would check which flight is cheaper to change in advance
only slim chance with this combination would be hand luggage only and running shoes
Last time I did separate tickets through Gatwick I had the choice of 3 or 8 hours....booked the 8 hour!