When I click on the link you gave for Dell batteries, it asks if I want to change to the UK site and when I click yes, it takes me to the Alienware homepage. The link I went to which only supplies adapters is here . I'm not sure if there is somewhere else on the UK Dell site I can find a battery for my laptop? Go to the profile page of Dell-Cares and click on Send this user a private message. Ask how you can buy a battery from Dell in the UK. parts people do ship to the UK, but they charge about $100 to do so. I also don't know if I'd be liable for any shipping taxes on top of that.  You might e-mail Parts-People to ask them. I vaguely recall someone saying that Parts-People had a European depot or retailer.
During a half hour game of Monopoly Madness when plugged in, the battery drained from 100% to 93% in my Alienware m15, which is three and a half years old. This is not a one off either. My understanding is that the battery should only discharge a maximum of 5% per hour when plugged in and gaming. After checking battery health on command prompt, it says that the battery still has 58,550 mWh of its initial 60,000 mWh maximum capacity, which is reassuring. I also did a battery check from within support assist and that passed. These last two facts seem to indicate my battery is fine, but I don't know enough about computers to know for sure. If I do need another battery, how do I obtain one? I looked on the Dell website and they only offer power adapters and no batteries for the M15. The only one I found that is made from Dell on Amazon is m15 battery But it is sold by a third party seller, which makes me apprehensive as I know you have to be super careful with lithium ion batteries. Is there a reputable seller of batteries for my laptop online which delivers to the UK? I will take it to the local computer repairs shop to fit if I need a new battery, but I would prefer not to buy from them too as I know they will charge more.  
m15 R1, battery replacement