40w Circular Flourescent Tubes - Daylight

Mechanicus

Hello.

I am looking for circular flourescent tubes for the lights in my livng room.
They need to be 15" Diameter, 1.5" thickness (roughly, it's not easy to measure whilst they are on the ceiling!)

They also need to be Daylight bulbs, or at a pinch, Cool White - not Warm White: I have these in at the moment, and they aren't bright enough. The light is only rated for 40w so I canot put in any 60w bulbs.

I have had a look around online, and the only websites that stock them charge £15 and up. I paid £6 for the Warm White bulbs, and I cannot see why these other ones should be so expensive.

Any help with this, or advice on where I could look would be appreciated.

Thanks in advance

-Paul

P.S. Sorry if there are any spelling mistakes. I am using my mum's laptop and I am not used to the key placement yet!