As always budget comes in to this a bit.
The difference in cost between a 1tb and 1.5tb is not that great, eg - a 1tb Iomega drive will cost the same as a 1.5tb Western Digital.
That doesn't mean WD are any less as good - it's just one of those things.
To be honest i have a WD plugged in the back of my iMac for use with Time Machine and 2x Iomega drives with which to provide original copies of files as they come out of a camera and then the tiff, h-res and web jpg versions of a processed file.
I've never had any issue with any of them, though i've had concerns over Freecom drives and tend to steer clear of them nowadays.
I suspect the comments you get will very much come down to peoples personal experiences.
Where to buy? Amazon can be quite good. If you look in PC World during a Bank Holiday sale they've been known to offer EHD's as loss leaders...
As for Mr B. - i would have to advise against a loft, purely because in most house fires & similar, that is nearly always the one area that gets trashed. Not sure what your broadband situation is, but you could have a second EHD connected wirelessly and only switched on for back up via synchronisation. That way there'd be no cables to give the game away and it needs only to be switched on when you download or have processed some pictures to back up, and can be stored in a cupboard or similar out of sight..
Finally, what is wrong with putting a second drive inside your computer upon which you can put all your pictures. This will give the best and fastest access, and then use a single EHD to back up to.
You might find that this way you could not only save a bit, which might allow you to take the 1.5or 2tb route - but it will give you exactly the same sort of security and still leave you main C drive empty.