Since the garage has identified that the coils are on the way out, if you are in the slightest way - mechanically minded, you could offer to change the ignition coils for your friend. Euro car parts sell them at around £15 each, with many ebay sellers able to beat this price including shipping.
http://www.eurocarparts.com/ecp/c/Renault_Megane_1.6_2004/p/car-parts/engine-parts/ignition1/ignition-coil/?413745111&1&537889b057bfe61d7c8229174fb0eeab317db9ec&000197
(you will need to make sure the ignition coils are for your friend's model/year Megane)
My wife owns a 1.6L (04) Megane - I have replaced 3 of the 4 coils due to failure (I have a spare, ready for the next).
Replacement is very easy - once you have removed the plastic engine cover, the low voltage leads to each coil can be removed with the aid of a small flat blade screwdriver. Each coil is held in place by a single retaining bolt (10mm head) - once removed, the coil can be extracted by hand, with re-assembly being the reverse process.
The only tricky part is that access to the coil retaining bolts is limited (some more so than others), such that you need to use an open-ended spanner, rather than a socket to get them out.