I do not like the fanless designs or the plastic cases, all mine have fans and are aluminum because I get scared that the HD will overheat, its already fragile since its being transported and inside a case so for me no fan is like tempting fate. I learned that after feeling how hot the retail ACOM Data drive I bought got
You can probably make your own cheaper then buying one already made (I like that option since I can personally choose the drive itself)
This is an example
http://www.newegg.com/Product/Produc...82E16817145230
Its aluminum and has a fan, the aluminum casing allows it to not heat up as much and the fan will keep it ventilated. There is a cooler looking one with a big fan on the top almost the size of the whole drive but I cant find it at the moment
All enclosures made in the last year "should' allow up to 400gb, with the falling price in drives on the market its pointless to spent $120-190 for a "retail" drive when you can get a enclosure for around $40 and then a big drive for around $60
Not sure if that is how it applies to the UK but in the US that is what I am some other people I talk with have gone since the retail drives that are firewire and USB are usually $$$$ than ones you could make yourself