www.ebuyer.com will supply most of this cheaper than local suppliers. Compare Ebuyer with
http://www.scan.co.uk/ for the best prices. I generally use Ebuyer but others swear by Scan.
What kind of volume do you think you will need from the printer/copier/fax?
You would save some dough (and desk space!) if you combine some of them. I would recommend spending a bit on a decent high volume B+W laser all in one fax/printer/copier then use the A3 for low volume A4/A3 posters/offers etc.
Something like this Canon is middle of the range, should be good for reasonable high volumes. Check for features like duplex/network card etc.
http://www.ebuyer.com/UK/product/117417 You will want something like this on the network so anyone can use it.
In terms of A3, we have had the old version of this Canon
http://www.ebuyer.com/UK/product/116581 for a couple of years. It does get through the ink but so do all decent inkjets. It does full bleed A3 which is great for posters. Under no circumstances consider a HP or Epson that still use 'tri-colour' cartridges instead of single inks. There is nothing more annoying that throwing away a cartridge that cost £50 and is still two thirds full! Our Canon uses 8 separate inks, but generally you'd only ever need to replace 2 or 3 cartridges on a big print run of say 20-30 A3 posters. (The carts are about £7 each)
With the external hard drive make sure they are both USB2 and Firewire, Firewire will come in useful at some stage.