A 5 foot fluorescent with a HF ballast is around 5400 lumen so with double tube fittings that would be around 41,600 lumen which is quite a lot of light, however one of the advantages or disadvantages if you don't realise is they are not fixed to a set wattage, in a long corridor where tubes are used to light every 5 meters or so, really don't need that much light, so fitting a tube giving 2200 lumen instead or 5400 lumen will not matter, it may be less than half the light, but don't need it anyway, but you can get LED replacement tubes same length which give out same as old fluorescent tube,
this 5 foot fitting is 50W it may look like a fluorescent fitting but it does not have a tube in it, the fitting is the whole thing, no tube required.
So today a 5 foot batten can be anywhere between 2000 and 10,000 lumen it is up to you. The link is £40 (4,500 lumen) and yours is £25 plus two tubes at £23 each for 18W so £71 in total, (4,400 lumen), both non corrosive so yours seems rather expensive. When you look around
this one costs less than the LED tube costs from
Wickes. OK I have no idea how good, but I have only bought two 5 foot LED replacement tubes for fluorescent fittings, reason for two was first one only lasted 18 months, and most of that time house was empty. OK came from
Screwfix not
Wickes and the second one is still working, but it is the only LED apart from toys I have needed to replace. Did have some 0.58 watt G5.3 MR16 lamps from Pound World fail, but at 0.58 watt really only toys.