Hi Tim, just noted your post.
Basically, there are 3 types of cracking which can follow from a chip; bullseye (where the laminate between the glass sections draws in air, and forms what looks like a bubble); starburst (where, as the name suggests - small spikes form in all directions from the central chip), and of course the crack.
All can be successfully repaired if the following criteria is met:
1. A repair is performed very soon after the chip occurs.
2. Moisture/dirt contamination is kept to a minimum.
If it is a crack type - anything longer than a cm, will be difficult to invisbly repair.
If you are shopping around for prices, I would suggest applying some superglue over the initial chip - this will provide some tensile strength to the screen, whilst limiting contamination in the laminate layer. Don't worry about blocking the chip - the repairer will need to drill an access hole to inject the resin in any case.
As Otto suggests, post a pic (including where on the screen its located), and I can advise further.
P.S. Regarding some companies charging £80 - I must be undercharging - I'm £30!
Hope that helps,