Carrying insulin on international flight

Looking for advice as I am sure this has been managed by others.

I will be travelling to UK next month. I need to carry two insulin cartridges (PEN fill types) with me. This is the first time I need to carry as in past medicines were sufficient.

End to end it will be roughly 16 hours i.e. when I take them out of Fridge (in India) and to the point I get next Fridge in Hotel (UK).

Q1. What is the best way (if any) to prevent denaturing insulin for \~16 hours? Are gel pack or pouch based storage cases works for such a long time? If not then what the next best alternative?

Q2. Is there any option to let Airhostess keep Insulin in some temperature maintained device in Aircraft during flight time?

Q3. Also I presume Insulin will be allowed to carry in hand baggage?

Q4. Can pharmacy in UK sell insulin to me if I show India issued prescription?

Thanks

Author: Own-Cup3180