Thanks for the replies guys, Simon I will take you up on that offer in the next few weeks, Joe, thanks for all the info pretty much exactly what I was thinking.
Another reason I wouldn't mind using the canister filter is the stand that the tank sits on isn't really suitable for a sump, would only be able to fit one around 15-20 litres anyway. Also can get the filter for a really good price and it's pretty much brand new, is there any good reason why I shouldn't use one?
I am also wondering what is it about that type of hob overflow box that people don't like, is it the noise they make because it's not a full syphon?