Its not necessary to use RO water for FOWLR but if you want a non-algae aquarium, dont want to cleaning your aquarium every week then i would advice to get RO water, its very cheap from your lfs and can be put straight into the aquarium rather than the need for dechlorinator. Its also alot better for the fish, inverts etc..
There's a shop I sometimes use at Bicester that lets you buy your canisters and then return them for an 80% refund. They also have an outlet at the m25 a41 junction if its any help. Used to be really good, but haven't been in a long while.
Thanks for the interest everyone. I have since purchased an Orca TL-550 which is 128 litres. I've gone ahead and put in 50 litres of RO yesterday and will be getting 50 more today...the hard way with a lot of muscle! How much do you guys pay for RO? When I used to run my freshwater planted tank with Discus I would buy it at ?3 per 5 gallon refill but now the same shops sell it for ?5 per 5 gallon.
I am now looking for Live Rock. My LFS is selling it at ?14.95 per KG which imho is too expensive. I have found an online supplier that is based near me who are selling it at half price but they are out of stock for a week. I am aware that Live Rock will displace a lot of water but I had no idea that it could do as much as 45 litres in a 128litre aquarium!
So if anyone can recommend a Live Rock retailer I would appreciate it!!! I want to get good quality so I don't mind paying extra for it. I trust my LFS and have seen the live rock they are selling in store aquariums for the past two weeks so I am confident that it is fully cured!