Jeanette JonesJust had the battery replaced on my 3 year old iPhone 6s Plus for £24.99
It was showing 81% capacity in Settings/Battery/Battery Health/Maximum Capacity.
I booked it through Apple using the link below and had it done through Carphone Warehouse in Portsmouth, (who I would NOT recommend for their Customer Service), and it took 2 hours, longer than normal as they only had 1 Engineer available that day.
Here’s some info for you:-
Apple Battery Replacement for £25, iPhone 6 and higher.
Only available at £25 until 31 December 2018
Info from uSwitch:-
Reason for offer:-
Book your appointment through here, https://getsupport.apple.com/?caller=arshw&locale=en_GB&storeID=R174&lat=50.903818&long=-1.406383
Get it while you can!