I need a replacement PL-11W, any ideas where to get one cheaper than the £15.00 they are asking for?

I've seen this one below but that's a "daylight" (£3.99) one and the bulb that I'm replacing is a red/white one.

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This not it:

AquaStyle 510 Aquarium Spares & Accessories - Buy Aqua One with confidence at Aquarium Parts

Aqua One PL-18W Sunlight / Tropical Mix

thanks, that site has a hell of a lot more than the one's I could find.

Not sure which one to go for now,

PL11W Marine Blue 20k Lighting Tube for AquaStyle 510 Aquarium or the

PL11W mix Triphosphor 7.1k & Blue 14k for AquaStyle 510 Original Aqua One replacement Triphosphor and Marine Blue Mix Flourescent Lighting Tube for AquaStyle 510

Brilliant Under Sea Effect....