Thank you so much Darnell0216.
After checking with my phone provider my battery was not covered under the warranty but I was offered a £10 credit against my account as a gesture of goodwill.
I ordered a new battery as I wanted to check if it was that causing the problem before having the phone sent away and reset. I bought the battery kit and when I tried to close the lid of the charger with the battery from my phone inside it would not close. The battery was severely swollen as you describe. I was shocked as I've only had my phone for two months.
I'm glad to have the problem resolved but I hate to think what could have happened had I left the battery in the phone.