Re batteries in checked baggage, see this link:
https://www.caa.co.uk/Passengers/Before-you-fly/Baggage/Items-that-are-allowed-in-baggage/
They won't allow Li-ion batteries in checked bags because of the fire risk - should be carried in your hand luggage. I've not had any issues in taking numerous batteries in hand luggage. I think I had 9 or 10 (inc my laptop battery) in my hand luggage from my T2 trip and was didn't face any issues.