Have a great time, wear what you feel comfy wearing,like everyone has said.
Saw Take That a few years ago atvthe football stadium Milton Keynes, were fantastic.
Im off to the Royal Albert Hall to see The Temptations and Four Tops this friday.
Im not sure what to wear i think it will get very hot in there.
Our hotel is 20 min walk from RAH will hopefully be able to cool down afterwards.
So many venues have no aircon, came out of a concert very hot and felt unwell, no aircon.
You will be fine ,as in the open.