Rather than buy an aquarium branded one look for ones made by phillips and osram etc.
They have similar colour outputs but are about a third of the price (£3ish+vat).
Postage starts off quite expensive (£10) but if you spend £9 on tubes it drops to £3
Plus if it breaks in the post they will keep trying. I had 3 replacements sent out, not due to poor packing just the way the courier treated them . Reminder to self Don't order tubes over christmas period again