About the cheapest spot drills in the UK I have found are here. Put a search in for all diameters and go to the bottom of the second page then the third.
http://www.engineeringsupplies.co.uk...11=192&12=&13=
They are very good quality, both the Cobalt and Carbide, and if not really abused, should last almost forever. For £20 to £30 you can kit yourself out with a decent range of sizes and angles up to 8mm, over that, as in all places, they get expensive.
I tend to use the 120 degree ones, as that almost matches the standard grind of a normal twist drill of 118 degs. For holes that have a countersink requirement, I use the larger 90 degree ones to do the countersink first, then drill down with a normal drill from that, two ops in one.
Hope this helps
Bogs