I got it 18 months ago, but when my pc went tits up I rang them to get a back up disk but they said I'd already got one issue so I couldn't get another one !

Does anyone know if these use "normal" Office setup disks, or the limited-use MDSN/Technet ones (usually brown in loose sleeves)? The two types use different product key sequences

If they are normal ones then you can legally download the ISOs from Digital River, and use them with your product key. If they are MSDN/Technet ones then I don't think theres an official M$ download link, though you can find them on The Pirate Bay (usual warnings apply)

In appearance, the backup discs look the same as discs often supplied with a new PC and are Orange (Office) Blue (Visio) & Green (Project)*. A white disc envelope with a DVD labled as a backup disc inside and a sticker bar code on the envelope. The software is initially downloaded using a key code supplied by email to a private email address. The process is not straightforward due to a software glitch on the download page. You have to 'add to your basket' and then click on your basket without waiting for the download bar to travel its course. Once the order has been placed, the reply (confirming acceptance) is not automated and some time may pass by before the operator sends her response. You also have to order Office as a single item order whereas Project and Visio can be ordered as a pair. For myself, a combination of telephoning the support line before and after placing my order helped oil the cogs.

You pay Microsoft direct not the agent however the agent is the gateway into the MS process by ensuring entitlement via a mod.uk email address. Service users without Dii access will not be able to process an application other than by proxy which is probably illegal. As I have stated previously; I did order backup discs at the same time which doubled the cost to approx £52 for three software downloads +discs. Office 2010 for a windows based PC, online download only would have been £8.95. Double that with a back-up DVD. The MAC software is Office 2011.

*The back-up discs are not in boxes and do not include documents.
MS Software Offer:

MS Office Professional 2010
MS Visio 2010
MS Project 2010

All at £8.95 instead of several hundreds of pounds each. The link is:

https://sabs.sbl.r.mil.uk which can only be reached by a Dii computer.

they sound like MSDN/Technet disks then. The ISOs from Digital River probably won't work. I don't think theres an "open" download for those from MS - you have to sign in as a member.
As I said before, they are listed as Torrents on The Pirate Bay, but that opens up a whole can of worms
Scarecrow's best bet is to get someone to provide a copy, and then use his product key with them

Office 2013 is available now for PC users (Mac users are still on 2011).

You can order direct from Microsoft though the process involves a few more steps.

Visit www.microsofthup.com/hupuk/home.aspx?culture=en-GB
Click "Don't know your programme code"
Enter your @mod.uk address
Wait for activation email to arrive.

Click on the link in the activation email and order Office 2013 for £8.95
Project and Visio 2013 are also available for separate purchase at £8.95 each.

Dii and EGS tends to mangle the Microsoft site so you may find it easier to forward the activation email to your home address and do the ordering there.

Edit: And SoftBox have now caught up so there's no need for the complicated process above. Office 2013 is available direct on https://sabs.sbl.r.mil.uk from a Dii computer.

Thanks for the external link stuff, it worked for me yesterday. The Dii link dies once you add office 2013 to your cart.