I've just bought myself some new XR4i drilled, grooved discs for my Velocity as a straight swap for my standard granada/sierra setup.

I want to replace the front calipers again with a straight swap. What Wilwood caliper is best and do I need a fitting kit or should they bolt straight on?

I have seen the Dynalites on Rally Designs for £79.95 are these worth getting or are they cheaper elsewhere? What else do I need?

As RD are a Wilwood distributor their prices are about as good as it gets. The Dynalites are a good choice (I chose them too) RD will probably have a bracket kit which will allow a straightforward fit to your uprights.