I'd still go for the OE leads I am afraid despite the cost. On the two occasions I have used them the connectors of the OE items (IME the items that tend to cause issues) were far superior (on my Mondeo the 'OE' Bosch and Magnecor leads required a hammer to get them to sit perfectly on the lead (read to physically 'click' into place in comparison to the Ford items). The Ford items were much easier to fit and didn't require such brutal action. Why can't people make decent pattern parts? Whilst the 4 pot may be better in this respect I really was impressed with how the 16v Beru leads connected onto the relevant bits on my S2. A positive and decent connection.
If you wish to put it into perspective Ford charge £130 for leads on a Mk3 Mondeo with a 4 Pot Duratec. I appreciate one can get £20 leads, but IME they barely last 20k before you get ignition issues (I.e Backfiring etc.), or harming something if other owners are anything to go by (I.e the ECU or coilpack). I shall admit in this instance £130 is a little rich... Magnecors are £60 on the same car, but why do they insist on using shit interconnectors? It's not like £60 is a small sum of cash to spend on HT leads!