I've been doing a lot of ordering at work, and I've noticed a couple of useful things:
OneCall is Farnell/CPC with the negotiated Higher Education discount (19% on most things, excluding things like test equipment), though it doesn't show the reduction until you're logged in with an institution-linked account. What's interesting is that staff and students of appropriate HE institutions can also get the discount for personal purchases (over 20 pounds value, ordered online, free postage). You just ring them up and give them an academic email address and they register you. First order must go to your home address, then they ship elsewhere.
So if you have any university connections or know someone who does, you can get substantial discounts...
Theo