Agree with Raffles that this is not a good plan. If the flight lands at 1130, it'll be more like 1200 by the time they're off the plane. I suspect the earliest they'll be at the AC in T3 is something like 1230. You should leave there by 1400 to get to T5 in time and to contend with any queues you'll face along the way. This gives you all of 90 minutes in a very unremarkable lounge. I do think you'll face some issues along the way of not having a T3 BP, but as I've never done this I can't say for certain. I'd skip it entirely and either go to the T2 arrivals lounge if it must be a lounge, or go straight to T5 and Plane Food.