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Given that your needs are mostly for photographic work, you would do well to get a fairly powerful one; picturtes and videoa are very demanding on resource, and the less you have, the slower it will operate. The crucial thing is to get lots of RAM - your 8GB suggestion would be a minimum, I'd t5hink, and the fastest processor that you can affford, although that is the most expensive bit.
The size of the memory you need (you suggest 1TB) will depend on the quantity you need to store; generally, I would have thought that 1TB would be enough, but you can always buy a standalone memory of any size, to use as an archive or back up perhaps. They work just like a giant memory stick. I am also a fan of Cloud storage, and there are many options; however you do need to remember that it is often a continuing financial commitment, unlike buying your own storage. Google offer a 5 GB free account
click here and there are many similar.
I assume that you already have software that you are comfortable with for manipulating the pictures? There is a huge range, from free to very expensive; it's not really my field, Adobe Photoshop seems to be the industry standard, I think.
Some details here.You also say: "We have also been advised that as the laptop comes with Windows 8 we will need to buy Microsoft Office software in order to open attachments on our emails. Is this correct?"
This is a baffling piece of advice. Nothing wrong with Windows 8, and you'll struggle to buy a laptop without it, unless you buy an Apple. You don't need Microsoft Office, even though most people do use it; You do need something like it, and if you are resistant to paying for it (and the cheapest package I can find is £170, although your new computer may come with a trial version on it, which you can convey to the full thing for about £100) then I recommend that you start by using
openoffice.org It is a completely free software suite that is very similar to and as compatible with Microsoft Office as makes no difference.