Thanks Chris for taking the time to send the links.
Unfortunately I have looked at both of them and they do not seem favourable.
The Ebay seller has no batteries for sale and the Amazon seller has too many negative reviews.
I have sent an email request to Samsung Support UK but have had no reply, yet..
Well, its better to change your battery on Samsung. I have bought some of them on Ebay and it runs out only in few hours. I guess they never sell their original battery to the outside and what they called as original is actually a fake battery that usually coming from China.
If at all possible I would rather pay a little bit extra and pay for a genuine product that (hopefully) has less chance of being faulty and (worse case) damaging my device.