As you are from London, I would recommend Big Al's or Sealife Central. These are your local fish stores (LFS). By purchasing from them they can continue to run a business in your city. Just ask
@EricTMah. If people keep buying online to save a couple of bucks, the stores close and people lose their jobs. Purchasing from the TFT members who are found under the "Store announcements" on this forum also keeps them giving advice and helping us all out. Not to mention the face to face of Frag fest.
All of my purchases are from TFT store members, LFS, and used equipment from other members on this site. My computer gives shitty customer service. I'd rather be able to ask advice from those who have "been there, done that".